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Power Vacuum Tubes Hand Book Jerry C. Whitaker

Vacuum Tube Principles

Publication details https://www.routledgehandbooks.com/doi/10.1201/b11758-4 Jerry C. Whitaker Published online on: 13 Mar 2012

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The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The publisher shall not be liable for an loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material. Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 Vacuum Tube Principles 3 impact of rapidly moving electrons or ions. This phenomenon is referred to referred phenomenonis This ions. or the rapidlyelectrons ofof moving impact result a as materials solid from surround ejected the are into also surface Electrons space. ing the from escape will contains it that electrons the sufficiently,heated of some is body solid a if that states emission monic ther of principle The tubes. vacuum in employed normally method the is electrons. associated of number the in and nucleus the in differences from arise elements chemical in differences The neutral. electrically is ofelectrons quota full a atomwith atom; the in an contained electrons of negatively the number to the charged equal charge positive a has which nucleus, heavier much a with associated electrons of or more one such composed Atoms are source. of their spective 10 × 1.59 of charge a and atom)10 × 9 of mass a have [1]. They matter all of constituents are that particles charged negatively minute, are Electrons Characteristics 3.2 industrial users. By far the most common are triodes and tetrodes. ityof the tube. Awide variety of tube designs are available to commercial and material used to construct the individual elements cationdetermine factorthe power capabil relative to the plate and cathode are the main factors that determine theof electrodes (grids) theycontain. Thephysical shape andlocation ofthegrids (the anode). Power tubes can be separated into groups accordinggrids that to the controlnumber the flow of electrons,and an elementproduceworkuseful[1]. that emittingsurfacean (the collects hasItcathode), the moreorone electrons powerdeviceAa isflow usingtubegridthe free electronsvacuum a of in to Introduction 3.1 Free electrons can be produced in a number of ways. of number a in produced be can electrons Free ( μ ) and other parameters of the device. The physical size and types of

of

Electrons −19 . lcrn ae las dnia, irre identical, always are Electrons C. −28 g (1/1840 that of a hydrogen a of (1/1840 that g Thermonic emission Thermonic amplifi 69 - - - - -

Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 electrostatic fieldmaterial. the theelectrostatic surface of at intense an by substances solid of out directly electrons pull to possible is it (orof electrons Finally, ions)be obtained. can emission before secondary the as 70 field can be expressed in terms of the voltage through which the electron the which through voltage the of terms in expressed be can field The velocity an electron or ion acquires in being acted upon by an electrostatic where where velocity not does the approach of that light: mechanics of fieldthe direction the tion in at a rate thatbethe calculated bylaws can of positive charge,respectively, involved. is negativeor a whether upon depending terminal, positive the away from or static fluxlines atthe point wherethe charge is located.The force acts toward electro the of direction the in exerted is electron or ion the uponforce This where charge a charged particle by an electrostatic fieldis proportional tothe product ofthe direction (toward the negative or cathode electrode).opposite the The forcein travel ions positively charged the while electrode, anode or ies[1]. bod Electrons, negativelybeing charged charged, tendother to travel as toward positive way the same the in field electrostatic an by exerted them forces upon have such, as and, particles charged are ions and Electrons Electron 3.2.1 or ions hydrogen mercury ions. as such origin, nated to according their desig derived.are Ions are they which atomorfrom molecule the resemble and electrons than heaviermuch are They weight,both. charge, or in maydiffer and alike all not are ions positive electrons, Unlike electrons. lost the of charge negative the to equal charge positive a and concerned, molecule atomor the weightof the having bodies charged havebecome so and trons Positive atomsrepresent ions or have that molecules lost one or more elec m F A accelera an causes particle charged the on exerts field the that force The e G F secondary secondary electron emission is the charge in C in charge the is is the force in dyn force the in is dyn force the in is is the voltage the is V/cm gradient in is the acceleration the cm/s is in is the mass in g in mass the is e of the particle and the voltage gradient

Optics , because it is to necessary have a source primary G F × = A = e m F × 10

7

Power VacuumPower Tubes Handbook G of the electrostatic field [1]: F exerted upon (3.2) (3.1) - - - - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 of light, the relationship between velocity and the acceleration voltage is (or ion) has fallen in acquiring the velocity. For velocities well below the speed Vacuum Tube Principles electron stream. electron power the fields on andtubes, magnetic other hand, focus the use to confine field, magnetic separately.consideredeach the ofsum field andforceelectric the from the thefrom forceresulting resulting vector the is electron the on acting force resulting the fields, magnetic and field.the through fieldmoving the theand electron of ofspeed magnetic the strength field will follow path. aThecircular radius circleisof this by the determined which in is the electron traveling, magnetic moving an electron a in uniform force field of magnetic the producesalwaysis the rightanglesthedirection at to that electron the of acceleration the Because path. curved a follow will velocity high a with field magnetic a entering electron an result, a force.As the and electron to the component of the fieldmagnetic that is producingthe of motion of direction to the both at angles right direction a forcein is, then, fieldin aat rightdirection angles tothe motion Theofthe resulting electron. magnetic the of component the of strength the and electron moving the by equivalentcurrent productthe of the to proportional forceis lar to the force it exerts on in a current an electric wire. The magnitude of the simi manner in a fieldnetic a forceaccordingly exerts onelectron a moving e ofmagnitude current electric an represents motion in electron An Magnetic 3.2.2 basis for ofthe understanding motionelectron a within vacuum tube device. a provides and valid nonetheless is information preceding exclusively, the almost simulation computer uses design tube modern While physics. sical achieve avelocity of approximatelywill of light. speed the one-tenth 2500 of difference potential a through dropping electron example,an For ions moveand Electrons at great velocities evenfields. in moderate-strength where is the magnitude of the charge on the electron and Magnetic Magnetic fieldsare notused for conventional powergrid tubes. Microwave electric both of action simultaneous the to subjected is electron an When section, relies on optics,Electron in this the principles as discussed of clas m e V v is the charge in C in charge the is is the velocity in cm/s velocity in the is to corresponding is the accelerating voltage the is is the mass in g in mass the is

Field

Effects v = 10 2 × × e V m × V 7

v is its velocity [1]. A mag ev represented represented ev , where, (3.3) 71 V - - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 ficient thermal energy energy to ficientthermal overcomefromescape thebarrier surface-potential suf [1].with activation Electrons thermal of result the as material a of face emission Thermonic Thermal 3.2.3 72 emitter. (After Terman, F.E., Terman, (After emitter. thoriated-tungsten a for temperature absolute of function a as emission electron of Variation FIGURE 3.1 temperatures. ous tity quan the by solely almost determined accordingly is appreciable becomes current electron the which at temperature The temperature. with emission in variation the of most for accounts equation the in term exponential The where surface, equationthe [1] to according the through escaping in must perform work ofthe electron measure an a is that related toa absoluteand quantity the material temperature of emitting the material. have to leavemoreenergy sufficient electrons because thetemperature with the surface of the emitted increases electron current material. thermally This A I b T is surface emitting an of area unit per released electrons of number The is the electron current in A/cm in current electron the is is the work an electron must perform in escaping the emitter surface emitter the escaping work must in the perform is electron an is the absolute temperature of the emitting material absolute the is emitting of temperature the is a constant (value varies with the type of emitter) (value aconstant is type the with varies b . Figure 3.1 plots from the a emission resulting cathode operated at vari Electron emission (A/cm2) 0.25 0.75 1.25 1.50 1.75 0.5 1.0 1000 0

Emission is the phenomenon of an electric current leaving the sur the leaving current electric phenomenon ofan the is 1250 Radio Engineering Radio

from Ca e thtempod 1500

Metals A I = 2 , 3rd edn., McGraw-Hill, New York, McGraw-Hill, , 3rd edn., 1947.) erature (K) T 2 1750 ε − T b /

Power VacuumPower Tubes Handbook 2000 2250 op Normal in po eratin t g (3.4) b - - - -

Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 Vacuum Tube Principles mary electrons. mary pri bombarding the of velocity the to equal nearly velocity a with emitted have relatively low velocity. However, are usually electrons a few secondary high as electrons alkali 5–10. as on primary to based secondary of surfaces ratios yield complex compounds Some metal 3. approximately to 1 from ranges than electrons less primary to secondary of ratio maximum the faces, sur metal pure With decreasing. then and a maximum reaching increases, electrons primary to secondary of ratio the velocity), higher produced consequently are electrons (and secondary potential low.is no However,increasing velocity with primary the when figure, the in being shown As surface the surfaces. composing and material is electrons the of bombarded. electron bombarding condition primary primary and the nature per of the velocity emitted the electrons by determined secondary [1]. of electrons electrons number energetic low-energy other The by emit bombarded will when insulators electrons) some (secondary and metals all Almost Secondary 3.2.4 the as known effect is emission field-assisted This escape. to electrons the cathode [2]. field This lowersthe barrier, surface-potential enabling more 1996.) in tals, fundamen tube C.D., Ferris, Electron (After structures. cathode and heater of types Common FIGURE 3.2 The majority of secondary electrons emitted from a conductive surface surface conductive a from emitted electrons secondary of majority The for power tubes. 3.2heater-cathode common Figure illustrates structures electron emission can Thermal be by increased applying an fieldelectric to . The Electronics Handbook Electronics The Figure 3.3

Emission illustrates a typical relationship for two types of of types two for relationship typical a illustrates , J.C. Whitaker (ed.), CRC Press, Boca Raton, FL, pp. 295–305, 295–305, pp. FL, Raton, Boca (ed.),Press, CRC Whitaker J.C. , co Oxid atin e g Schottky 73 - - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 74 trons gained from all sources equal to the number of secondary electrons electrons emitted. secondary of number elec the to of equal number sources all the from makes gained trons process This electrons. significant a secondary itself of the into number back until or attracts it that electrons, positive bombarding sufficiently is the of surface velocity the in result a as increase unity the to of decreases electrons primary to secondary of ratio the that positive sufficiently is surface the until continues action This positive. increasingly becomes surface the arrive; they than faster emission ondary sec primary through to electrons loses surface secondary insulating the of unity, exceeds ratio electrons the when extreme, opposite negative the In more action. become a blocking in to resulting insulator electrons, primary the the of most repel to finally, and, causes This depart. than arrive electrons more because charge negative net a acquires insulator the unity, than less is current primary to secondary of ratio the If bombardment. the by affected is metals. bombarded being for surface as insulating lines the of same potential net The the along follows potential electron primary of electron primary of function a as current primary velocity. F.E., Terman, (After to current emission secondary of Ratio FIGURE 3.3 For insulators, the ratio of secondary to primary electrons as a function function a as electrons primary to secondary of ratio the insulators, For

Ratio of secondary electrons to primary electrons 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 0 0 100 200 Radio Engineering Radio 300 400 A voltage pplied 500 , 3rd edn., McGraw-Hill, New York, McGraw-Hill, , 3rd edn., 1947.) 600 700 Power VacuumPower Tubes Handbook 800 900 1E3 O Ba Ni - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 A tube is, therefore, designed with the elements necessary to utilize elec utilize to necessary elements the with designed therefore, is, tube A are of Electrons no value in a vacuum they tube can unless be put to work [3]. Types 3.3 Vacuum Tube Principles Boca Raton, FL, pp. 1996.) FL, 295–305, Boca Raton, Ferris, (After cathode. in heated fundamentals, tube C.D., indirectly Electron (b) and cathode heated directly (a) diode: Vacuum FIGURE 3.4 the neutralize ofeffects the plateto voltage are necessary repelled into the cathode bynumber the negative the space of excess in electrons the All leaving cathode. just electrons the upon plate positive the of attraction the izes the exceed producenegative a will that cannot number instant any at plate and cathode the between transit in electrons of number the because occurs capable.This is cathode the which therefore, voltage. anode upon depends cathode rather temperature than The anode current is then emitted. limited by are the they electron as emission rapidlyof as the cathode cathode the and, from drawn are electrons high, positive anode is shown in tube. the flows. through negative, no current and is anode the When electrons it the repels passes therefore, current, electrons; attracts it positive, is anode the when because rectifier a inherently is tube a 3.4).Such Figure (orplate) anode [1] an by (seesurrounded emission, thermonic by electrons emits cathode,which a containing tube vacuum two-electrode a is diode A Diode 3.3.1 cathode. the of surface movement allow free and to of prevent the electrons damage to the emitting envelope to the removed connections from is air The seals. necessary airtight broughtout through the having envelope electrodes evacuated The an in electrodes. enclosed supplementary are more or consist one elements and These cathode them. a produce of to required those as well as trons At low anode voltages, however, plate current is less than the emission of emission the voltages,than anode lowAt however,less is platecurrent anode relationship between voltage The typical flowingand current theto supply voltage (a) Filamen

of t

Vacuum – + Filamen Elec

Tubes t Figure 3.5Figure tron flo Pl ate supply voltage The Electronics Handbook Electronics The – + w . When the . anode the voltageWhen is sufficiently space charge space Pl at e ) (b Ca He , which completely which neutral , e thod ater , J.C. Whitaker (ed.), Press, CRC J.C.Whitaker , Pl at e 75 - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 76 ac supply voltage to the dc voltage(s) necessary for other devices Diodes in arecommonly the rectifiersusedasunit [3]. in ac-powered systems to convert the Applications 3.3.1.1 tube. of the radiated walls to the result of the impact and appears at the anode in the form of heat that must be heata into as transformed then is energy kinetic anode, this the strike trons elec moving swiftly these energy.When kinetic into converted is it anode; travelinginfromthe first expended thecathodeaccelerating electrons theto cathode.the into back fall will and negativecathode the field the adjacentby stop to a to brought be velocities)will emission low having electrons (those remainder The plate.positive the toward drawn are they where region the reach and cathode the near field negative the penetrate will emission of velocities est high the having electrons those cathode. the drivenback Only sion into are emis lowofvelocity a having movethose cathode, they away and the from The negative field next theto cathode tothe causes electrons slow emitted as the cathode are projected out field into emission withthis velocities. varying from emitted electrons The cathode. the to respect with potential negative is sufficient togive the spaceinthe ofimmediate vicinity the cathode a slight cathodeplate the the and between transit in negative of electrons the charge cathode. of the emission independent electron of the substantially is by plateand way potential determined by spaceis platethis charge, current many excess the electrons cathode emits. how When the of plate current is irrespective limited in applies situation this transit; in electrons the of charge tem cathode F.E., Terman, (After three peratures. for tube two-electrode a in voltage anode of function a as current Anode FIGURE 3.5 The energy that is delivered to the tube by the source of anode voltage is anode of source the by tube the to delivered is that energy The the that reveal will situation space-charge the of examination Detailed Increasing plate current Increa sing plate voltage Radio Engineering Radio , 3rd edn., McGraw-Hill, New York, McGraw-Hill, , 3rd edn., 1947.) Power VacuumPower Tubes Handbook Ca Ca Ca oxide-coat (tungste e thtempod e thtempod e thtempod dashed line) dashed s = n emitte ed olid line, erature erature erature = r T T T 3 2 1 - - - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 Vacuum Tube Principles shield. It allows some, but not all, of the electrostatic flux from the anode anode the from flux electrostatic electrostatic the imperfect of all, an not but as some, allows It functions shield. effect, in grid, The plate. cathode the the and of vicinity grid the the between pass that in of electrons number the field controls therefore, and, electrostatic the affects negative is it which to extent [1]. the However, electrons no attracts so and cathode the in illustrated as tube, the of line center the along cylinder each of axis the with mounted are and shape in cylindrical are anode the and grid, the or structure, cathode filament The symmetrical. cylindrically are tubes Most plate. and grid, controlcathode, the elements: internal three generators.haveTriodes RF of The power triode is a device three-element commonly used in a wide variety Triode 3.3.2 pentodes. and tetrodes, triodes, of operation the understanding in important however, operates,is voltage—has of how diode supersededby acthe solid-state been understanding devices. An an rectify diode—to tube vacuum a of function basic The input fied producedoutputalternating current an voltage. by 3.6aFigure shows the basic diodeand 3.6bFigure circuit the recti illustrates circuit. rectifier a (After of characteristics current (b) and circuit (a)functioning circuit: diode Basic FIGURE 3.6 (a) Ele The grid normally is operated at a negative potential with respect to to respect with potential negative a at operated is normally grid The configurations: two are commonly in availableprimary tubes Rectifier • • Ca ctr e thod RCA Receiving Tube Receiving RCA Manual rectifier applications rectifier Two plates and one or two cathodes the same devicein for full-wave plateOne one cathode and for half-wave applications rectifier on flow Pl – at e A + Figure 3.7Figure Pl – ate curr A B . en + , RC-30, Radio Corporation of America, Camden, NJ, 1975.) Camden, of America, , RC-30, Corporation Radio t tput Ou ) (b

Plate current voltage input Alternating output curren output characteristic Pl Re ate volt e Diod ctified s t 77 - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 78 where quantity to the cathode proportional is cathode. the near produces tials poten and plate grid the of action combined the that field by a electrostatic determined the in purposes, current practical all space for is, the tube vacuum that is result three-electrode The interval. only for time charge additional it space brief the region, to a contribute this to beyond as quickly traveled so plate has the electron reaches an After vicin cathode. immediate the the of in ity electrons the of solely plate, the almost toward consists transit in therefore, electrons the interelectrode of the charge of space total remainder The the space. in low and cathode the near large is rate of flow to the proportion in of electrons density volume the that is tion condi of this result plate. The the toward distance some have traveled that electrons the with slowly compared moving are cathode the near electrons the because results phenomenon This effect. little has space interelectrode the of rest the in field the cathode; the near field electrostatic the by solely almost determined is conditions space-charge-limited under tube triode a in anode the reach that electrons of number The wires. its between leak to μ E E field the symmetrical, is structure grid the When is a constant determined by the geometry of the tube of the geometry by the determined a constant is b c is the control grid voltage control grid the is to (with cathode) respect is the anode voltage anode the is to (with cathode) respect Mechanical configuration of apowertriode. configuration Mechanical FIGURE 3.7 E E b c + μ

Power VacuumPower Tubes Handbook Tube base E at the surface of the the of surface the at surrounded bycontrol Filament atcenter grid Plate (3.5) - - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 tion factor. tion The amplifica the determines plate and cathode the to relative grid control the cathode. of Placement the of surfaces the fields at electrostatic producing in voltages. It is a measure of the relative effectiveness of grid and plate voltages constant The Vacuum Tube Principles in grid voltage swing to drive up the zero grid voltage point on the curve. curve. the on voltagepoint grid zero increase the up drive corresponding to voltageswing a grid in is there bias, increased this With voltage. plate given some at off current plate the cut to 304TL the for required voltageis the grid into driving the positive grid region. Note howalso much more bias rent at agiven plate 304TL the voltage from ( obtained be can the plots 3.8b Figure same parameters for plotted. a tube with a parameters the between relationship the of newequipment, in provides example common a notused while and, design voltages grid ous a with for triode a of plate voltage3.8a function a Figure as plots plate current at grid vari and where from determined be can ideal of triode an cathode current total The where following: include relationships the ematical μ E E I I E E S R μ k b is the amplification the factor is amplification the factor is held(with plate current constant) m b b c c is the cathode current the is is the total instantaneous plate current instantaneous total the is p 1 is the grid voltage grid the is is the plate the is voltage plate voltage instantaneous total the is is the dynamic plate dynamic resistance the is is the transconductance (also may denoted be transconductance the is is the total instantaneous control grid voltage control grid instantaneous total the is μ , the amplification factor, is independent of the grid and amplification factor,plategrid the independent , the is of μ , values of triodes generally range from 5 to 200.to 5 Key math from range generally values, oftriodes E I c k + = S R = μ μ ⎩ ⎨ ⎧ m p of 20. Observe how much more plate cur μ = = of 12 [4]. 304TL,a tube, The classic a is Δ Δ Δ Δ Δ Δ E E E E E I I μ c b b c b 1 b b 1 ⎭ ⎬ ⎫

2 3 /

G m ) μ =12) without (3.7) (3.8) (3.6) (3.9) 79 - - - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 80 Laboratory Staff, Staff, Laboratory a with (a) triode: a for characteristics Constant-current FIGURE 3.8 ) (b (a) –300 –200 –100 Grid voltage –500 –400 –300 –200 –100 Grid voltage 100 200 300 400 500 500 100 200 300 400 0 0 0 0 500 The Care and Feeding of Power Grid Tubes Grid FeedingPower of and Care The 500

2.2 2.0 1.200 1.0 1000 1.000

1000 1.8 .900

1.4 .800 .700(A) current Grid 1.2 .600 .500

100 .400 1500 Grid current (A current Grid .300 800

1500 .100 200 600 0 750 500 500 400 300 2000 200 2000

125 ) 150

075 2500 0 100 50 Pl Pl 2500 ate volt ate volt 75 3000 50

050 3000 age age

100

125

100 3500 , Varian Eimac, San Carlos, CA, Carlos, 1984.) San Eimac, , Varian Power VacuumPower Tubes Handbook

075 μ

075 of 12 and (b) with a with (b) and 12 of 3500 4000 constant curren constant cons characteristic characteristic Eimac 304TH Eimac 304TL 0 ntta 4000 4500 curr 4500 5000 en s s 70 50 t 60 40 35 25 30 15 20 t 10 500 250 μ 5000

5500 Plate current of 20. (After (After 20. of (A)

1.00 1.50 2.00 2.50 3.00 3.50 4.00 5.00 6.00 7.00

0 250 500 6000 5500 Plate current (A) Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 the operating bias is zero, as depicted in Figure 3.9. These 3.9.These Figure in depicted as zero, is bias operating the High- oscillators. and fiers 3.8a Figure b. and comparing Low- Vacuum Tube Principles Grounded-grid constant-current characteristics for a zero-bias triode with a with Staff, Laboratory triode zero-bias a for characteristics constant-current Grounded-grid FIGURE 3.9 is structure grid The conditions. adverse under operation for intended no-loadunder conditions. rise current to given be must considerations extra applications,but heating a with triode a than triode a of current a with grid The load. changing a with variation grid-current lower exhibit tubes Such into. works normally oscillator heating dielectric or induction an that load in variations wide the of because applications ing limited. is triode zero-bias the of use present-day attributes, these Despite needed. are drive or bias of loss for circuits protection no Furthermore, source required. power is bias No simplicity. The circuit amplification. and gain grounded-grid power good offers in tube used is commonly triode 400 zero-bias of ratings dissipation plate with available are Triodes with a with Triodes Vacuum tubes specifically designed for induction heating are available, are heating induction for designed specifically tubes Vacuum medium- and Low- Filament-to-grid voltage –200 –100 –125 –150 –175 μ –25 –50 –75 +25 tubes have lower voltage gain by definition. This fact can be seen by seen be can fact This definition. byhavelower voltage gain tubes μ 0 of 20 will rise substantially less under a light- or no-loadcondition light-or a under less substantially rise will 20of 0 The Care and Feeding of Power Grid Tubes Grid FeedingPower of and Care The μ 1000 of 20–50 generally are used in conventional RF ampli RF conventional in used are generally 20–50 of μ μ of 40. High- 40. of eie uuly r peerd o idcin heat induction for preferred are usually devices μ triodes (200 or more) may be designed so that that so designed be maymore) or (200 triodes 2000 Pl ate- μ triode oscillators can be designed for designed be can oscillators triode to-g 600 3000 rid voltage 200 100 050 400 , Varian Eimac, San Carlos, CA, Carlos, 1984.) San Eimac, , Varian 4000 ty W–10 pical constant curren constant pical characteristic gr Eimac 3-400Z Grid current (A current Grid Pl gr ounded ate curr kW or more. The The more. or kW 5000 zero-bias triodes zero-bias ent (A μ id of 200. (After (After 200. of s 0 .100 .200 .400 .600 .800 1.00 1.80 2.20 1.40 ) ) t 6000 81 - -

Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 82 The principal advantages of a tetrode over a triode includea theshield following: or screen between the input circuit and the outputbehind circuit the control-gridof the tetrode. bars, as observed from the cathodecontrol surface, grid and andserve the as anode. The grid bars of numbertheofvertical screenelements grid(bars) thecontrolasare gridmountedismounted between the directly same purpose as the grid in a triode, while a second ( The tetrode is a four-element tube with two grids [4]. The Tetrode control grid serves3.3.3 the easy waveguidefor and resonators. coaxial into integration arranged are triode planar the of surfaces contacting The modes. inductance. triodes Planar are used in both lead reduces which lengths, lead short in results triodes planar of struction 3 to (up frequencies high at used be to tube electron reduces spacing close The frequencies. are constructed so 3.10. called Tubes Figure in shown as surface, flat a of shape load. dissipation load increases. grid the As decreases, with ­ruggedized ample dissipation capability to deal with wide variations in TubesGrid Staff, Laboratory triode. (After a planar of configuration Internal FIGURE 3.10 Triodes also are manufactured with the cathode, grid, and anode in the the in anode and grid, cathode, the with manufactured are also Triodes • • • modulation distortion. inter low and radiation spurious little with equipment ple,flexible Moreefficient operation. the of compact,allowdesign Tetrodes sim supplyneed 1% only output of the power. circuit driving the cases, most In powerrequirements. driveLower plate-to-grid feedback. Lower internal planar triodes planar , Varian Eimac, San Carlos, CA, Carlos, 1984.) San Eimac, , Varian Control Filamen Ca Ano e thod gr de . This construction technique permits operation at high high at operation permits technique construction This . id t continuous wave GHz or so). The physical con physical The so). or GHz Power VacuumPower Tubes Handbook rni time transit screen Grid contac The Care and Feeding of Power Power of Feeding and Care The ) grid with the same (CW) and pulsed Low-inductan base contbase t , allowing the the allowing , ac t ce - - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 Vacuum Tube Principles ls AB class 3.12 Figure Application Example 3.3.3.1 to expected. be performance to categorize roughly the useful is amplification factor screen the applications, tetrode most In amplifier. RF value of screen arithmetic the The where of amount plate the current. mine device constant-current a considered be can therefore, tetrode, voltage.plate The in change a cause not does plate current in change a tetrode,idealvoltages. an grid various In plots of plateplate as a function current voltage at a screen fixedvoltage and 3.11 Figure tetrode. plateofvoltagea independent almost in is Platecurrent Handbook (eds.), voltage, plate Christiansen D. of and D. Fink, function (After a shown. as as voltages grid plotted with is current Plate characteristics. current plate Tetrode FIGURE 3.11 E μ μ E E K I by determined is ideal of tetrode an cathode current total The k p s b c c is the cathode current the is is a constant determined by tube dimensions by tube determined aconstant is is the screen amplification factor screen the is 1 is the plate the is amplification factor 2 is the plate the is voltage is the control grid voltage control grid the is is the screen grid voltage grid screen the is Plate current (A) 0.2 0.4 0.6 0.8 1.0 1.2 , 3rd edn., McGraw-Hill, New York, McGraw-Hill, , 3rd edn., 1989.) 0 1 0 or class C power amplification. The device is particularly well well particularly is device The amplification. power C class or shows a radial beam power tetrode (4CX15000A) designed for for (4CX15000A)designed tetrode power beam radial a shows 200 E c2 . The voltages on the screen and control grids deter grids control and screen the on voltages The . = 300 V K I 400 k + = Pl ⎩ ⎪ ⎨ ⎪ ⎧ ate volt E μ c 1 generally is not used in the design of the generally notin an is used 600 s E E μ μ c s 2 + b p 800 ⎭ ⎪ ⎬ ⎪ ⎫ 2 3 /

1000 Electronics Engineers’ Engineers’ Electronics –50 V –40 V –30 V –20 V –10 V 0.0 V E c1 +10V = (3.10) 83 - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 84 and applyand tube/socket/chimney to the approximate combination. are shown values drop Pressure direction. base-to-anode the in passes air which in table the apply in given designs to figures 225°C. The of temperature anode maximum a atand 50°C air cooling the with tube the dictates that a factorsafety be provided. practice engineering good 250°C, is anode the and seals for rating perature socket and contact fingers base at athe safe operating keeps temperature.Although thetube tem maximum the of base the around air cooling of ment chimney. Adequate moveair an by fins cooling anode the to guided is and socket the through passes air cooling where compartment pressurized a in mounted is socket tube The applications. all in cooling forced-air requires voltagesandscreen are present. filament while rent. Plate voltage, plate loading, and/or bias voltage must never be removed grid, screen dissipation is the product of dc voltagescreen and dc cur screen by the product of the dc grid current and the peak positive grid voltage. occurs. arc internal an case in energy supplypower stored absorb help to anode tube the with series in inserted is typically resistance protective A voltage.plate high at occurring arc nal cooling. high air and is 15 ruggedness tube the of dissipation plate rated mechanical maximum The efficiency. for filament mesh thoriated-tungsten heated directly a has tube The service. power amplifier linear RF for suited Devices, Electron AL.) Svetlana Huntsville, of (4CX15000A). tetrode (Courtesy power beam Radial FIGURE 3.12 The 4CX15000A must be mounted vertically, base up or down. The tube tube The down. or up base vertically,mounted be must4CX15000A The 450 is dissipation maximum grid Screen The maximum control grid dissipation is 200 inter an from result may that damage from protected be must tube The Table 3.1 W. With no ac applied to the the to applied ac no With W.

W, determined (approximately) Power VacuumPower Tubes Handbook lists cooling lists parameters for

kW using kWusing - - - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 Vacuum Tube Principles specifications are listed in listed are specifications shutdown to cool properly. tube to allowthe voltage and turn-on, normally should continue for a brief period (5 1.46.by increased are drop pressure and 10,000 at 1.20; of factor a by increased are drop pressure At 5,000 cooling. for equivalent Devices, Electron Svetlana of (Courtesy tetrode. 4CX15000A AL.) Huntsville, of dimensions Principal FIGURE 3.13 An An outline of the principal tube is dimensions given in Figure 3.13. General applied is cooling base Anode and before or simultaneouslyfilament with increased be must rate flow the level, sea above significantly altitudes At Note: Dimensionsshownareappr 233 mm Source: 15,000 12,500 Plate Dissipation(W) 4CX15000A Power Tetrode Level at Sea the for Requirements Airflow Cooling Minimum TABLE 92 mm 7,500

3.1 Courtesy ofSvetlanaElectron Devices,Huntsville, AL. 120 mm 66 mm

Table 3.2 oximate.

ft above sea level, both the flow rate and the the flowand rate the level, above both sea ft Airflow (CFM) . 192 mm 645 490 230 Ano 22 mm de ca de Filament conne (Inches p Pressure Drop Sc Control re Ano en gr 4.6 2.7 0.7 of Ano de

Water) gr ft, both flow rate flow both ft, id ctions id de airchanne

min) min) after l 85 Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 86 Source: Plate outputpower Plate dissipation Calculated drivingpower Peak RFgridvoltage DC gridcurrent DC screen current DC platecurrent DC gridvoltage DC screen voltage DC platevoltage Typical operation(frequencies upto110 Grid dissipation Screen dissipation Plate dissipation DC platecurrent DC gridvoltage DC screen voltage DC platevoltage Radio frequency poweramplifier(classCFM)(absolutemaximumratings) Base type Cooling method Maximum operatingtemperature (seals/envelope) Operating position Net weight Diameter Length Mechanical characteristics Maximum frequency forfullratings(CW) Direct interelectrode capacitance(grounded grid) Direct interelectrode capacitance (grounded cathode) Amplification factor(average),gridtoscreen Filament current Filament voltage Filament type Electrical characteristics 4CX15000A of the Power Tetrode Characteristics General TABLE

3.2 Courtesy ofSvetlana Electron Devices,Huntsville, AL. MHz) 26.7 8.1 220 730 0.30 0.59 4.65 −510 750 7.5 C C C C C C Power VacuumPower Tubes Handbook out in gk out in pk kV dc W V V dc A dc A dc A dc V dc 25.8 158 4.5 164 A (at6.3 6.3 ±0.3V Thoriated-tungsten mesh 36.5 9.0 220 790 0.27 0.54 4.55 −550 750 10.0 200 450 15 5.0 −750 2,000 10,000 Coaxial Forced air 250°C Axis vertical,baseupor 5.8 193 238 110 0.21 25.6 67 1.3 down kW pF A kW kg (12.8 pF MHz pF W V V dc W W mm (7.58 mm (9.38 A dc A dc A dc pF kW kV dc pF pF V dc V V V lb) V) in.) in.) Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 these dislodged electrons usually do not cause problems because no posi no because problems cause not do usually electrons dislodged these suffi at types, moving if may, three-electrode [3]. and plate two- In electrons other the dislodge speed, cient striking electrons tubes, electron all In Pentode 3.3.4 Vacuum Tube Principles where equation space-current total same The applies tetrode: the pentode towith the as tetrode. the in than current on plate effect less even has voltageplate pentode, the of design the of Because the include tetrode the over following: advantages main pentode’s The plate. and screen the between interchanged being from electrons secondary prevents produces grid suppressor The anode. the and third the The grid, tetrode. a in as function same the perform grids screen and trol tetrode. effectreduces the plate current and limitstheplate useful voltage swingvoltage. for a screen-gridThis the than lowervoltageplateswings the if so larly particu electrons,secondaryand theseattractionstrong plate to offersathe emission. secondary called is cathode the from by electrons electrode of an bardment These bom by caused them. Emission plate. the to attract back drawn to are therefore, present electrons, is itself plate the than other electrode tive E μ μ E E K I grids three The pentode [4]. incorporating is tube a five-electrode The con thecaseIn of screen-grid tubes, theproximity of thepositive screengrid to • • • k p s b c c is the cathode current the is is a constant determined by tube dimensions by tube determined aconstant is is the screen amplification factor screen the is 1 is the plate the is amplification factor 2 is the plate the is voltage is the control grid voltage control grid the is is the screen grid voltage grid screen the is put for agiven plate operating voltage. outpower higher slightly allows This dissipation. excessivescreen voltagewithout screen the below voltageswing plate let to Ability linearity.Good effects. emission Reduced secondary suppressor grid suppressor , is mounted in the region between the screen grid grid screen the between region the in mounted is , K I k + = ⎩ ⎪ ⎨ ⎪ ⎧ E c 1 E E μ μ c s 2 + b p ⎭ ⎪ ⎬ ⎪ ⎫ 2 3 / ptnil minimum potential a

, which which , (3.11) - 87 - - - - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 amplitude modulation. The required modulating power is low because of because low is power modulating required The modulation. amplitude of Because grid. ability, suppressorthis a modulating voltage the be can applied to the suppressor on to achieve potential the varying by current plate cathode. It may be operatedalso at cathode It potential. possible is to control The suppressor grid may be operated negative or positive with to respect the 88 of Svetlana Electron Devices, Huntsville, AL.)of Devices, Huntsville, Electron Svetlana (Courtesy device. pentode power 5CX1500B FIGURE 3.14 voltagemodulated, is screen the If current. voltagescreen and screen of uct pation, in wherecases there is no ac applied to the is screen, the simple prod voltage. grid positive operation. safe peak and ensure Table will 3.3 in current listed those near levels drive grid and bias at Operation dc of product the mately life. tube maximum for value rated the of ±5% to maintained is socket, the at sured Table3.3 in given are tube the for 3.14. Figure specifications in Basic shown is device a as use for designed AB class pentode power ceramic/metal a is 5CX1500B The Application Example 3.3.4.1 suppressor. of interception low the the electron The The power dissipated by the screen grid must not exceed 75 25 is grid control the of dissipation rated The 5.0 for rated is 5CX1500B the of filament The 1 . linear amplifier or FM VHF amplifying device. The exterior of the of exterior The device. amplifying VHF FM or amplifier linear Power VacuumPower Tubes Handbook

V. Filament voltage, mea voltage, Filament V. W. This value is approxi is value This W. W. Screen dissi - - - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 Vacuum Tube Principles Filament type Electrical characteristics 5CX1500B of the Power Pentode Characteristics General TABLE Peak RFgridvoltage Grid current Screen current Plate current Grid voltage Screen voltage Suppressor voltage Plate voltage Typical operation(frequencies to30 Grid dissipation Screen dissipation Suppressor dissipation Plate dissipation Screen voltage Plate voltage Radio frequency linearamplifier(classC,CWconditions) Net weight Maximum dimensions Maximum operatingtemperature Operating position Recommended (air)chimney Recommended airsystemsocket Base Cooling method Mechanical characteristics Frequency (maximum)CW Direct interelectrode capacitance(grounded cathode) Amplification factor(average),gridtoscreen Transconductance (avg.), Filament current Filament voltage maximum ratings

3.3 I b =1.0 A dc, MHz) E c 2 =500 V dc Diameter Length Feedback Output Input 255 35 94 900 −200 500 0 3000 mA dc mA dc V mA dc V dc V dc V dc 75 5.5 24,000 38.5 5.0 ±0.25 Thoriated-tungsten mesh 255 34 88 900 −200 500 0 4500 25 75 25 1500 750 5000 850 85.6 130 250°C Axis vertical,basedown SK-806 SK-840 series Ring andbreechblock Forced air 110 0.20 17.8 or up pF mA dc mA dc W W W MHz V mA dc V dc V gm (30oz) mm (5.2 A (at5.0 mm (3.37 pF pF V dc W V V dc μ mhos V in.) V) in.) ( continued 89 ) Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 90 grids account forgrids approximately 350 and suppressor) of combined. case the 5CX1500B,In the heaterthe and three power to the equal dissipated byplate, the heater, (control, grids and screen, requirements for the pentode. Note that the power dissipated by the device is airflow the Table 3.4lists section. previous the in 4CX15000Adiscussed the used be not fuse. should a as it develop; may that currents surge the withstanding of capable be should resistor The sufficient. is plate and supply power the 10–25 of resistance current-limiting A tube. the inside arc an of event the in current surge against protected be should circuitry associated for mostsor grid applications. suppresvoltage the zero ofoperationfor designed been 5CX1500B has The in specified conditions operating ortypical nearlyzero for zero all event failure. of acircuit dissipation must toprotective provided be 75 screen means to limit or plate load are removed with filamentand screen voltages applied. Suitable dissipation is likely to torise excessive levels if the plate voltage, bias voltage, dissipation screen depend will on the and current rms screen voltage. Screen Plate inputpower Calculated drivingpower 5CX1500B of the Power Pentode Characteristics General TABLE Source: Plate outputpower Plate dissipation Mechanical dimensions for5CX1500B the dimensions given in are Mechanical for as 5CX1500B forthe lines same follow requirements the along Cooling 1500 is 5CX1500B the of rating dissipation plate The 25 is suppressorrated grid dissipation ofthe The

3.3 Courtesy ofSvetlanaElectron Devices,Huntsville, AL.

( continued Source: At 6000 At sealevel Plate Dissipation(W) 5CX1500B Power Tetrode the for Requirements Airflow Cooling Minimum TABLE

ft 3.4 Courtesy of Svetlana Electron Devices, Huntsville, AL. ) 1550 1000 1550 1000 Airflow (CFM) W dissipation. 58 33 47 27 1980 720 2700 9.0 Power VacuumPower Tubes Handbook W W W W W. is Suppressor current Drop (Inches of Water) Pressure 0.95 0.40 0.76 0.33 3180 870 4050 9.0 Figure 3.15Figure

W. The tube and and tube The W. W W W W

Ω between between Table3.3 . W in the the W in - . Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 Vacuum Tube Principles tion is almost universal. As the operating frequency is increased beyond beyond construc increased is planar frequency operating the frequencies, As higher almost universal. At is tion form. in cylindrical invariably tube. of the capability power-handling the reduces This used. be must electrodes sized smaller- and spacing closer increased, is frequency operating device.the As effects. transit-time reduced exhibit region grid-to-cathode the in spacing spacing. Tubes ages respective at and their and anode grid the reduced with volt accelerating the of function a is point This significant. become effects a point increases, is ing atfrequency reached transit-time which the electron space the traverse to travel and grid, the cathode, the on electrons from to through plate.the As operatthe by taken is time finite A tubes. electron of Electron [5]. limit designed its beyond increased is frequency operating the as rates deterio tube vacuum given a of performance devices, active most with As High-Frequency 3.4 Principal dimensions of 5CX1500B pentode. (Courtesy FIGURE 3.15of Svetlana Electron Devices, Huntsville, AL.) Gridded tubes at all power levels for frequencies up to about 1 about to up frequencies for levels power all at tubes Gridded a of limit high-frequency the with interrelated is also limitation power A 127 mm transit time transit Figure 3.16Figure is a significant factor in the upper-frequency limitation limitation upper-frequency the in factor significant a is illustrates the relationship. the illustrates

Operating 48 mm 85 mm

Limits 20.6 mm Filamen Filamen Control Sc Suppr Ano re en gr de essor grid grid essor Contact surface Contact t t gr id id

GHz are are GHz 91 - - - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 92 in their basic design. their in and Klystrons other microwave take advantageactually tubes of transit time 100 at below 30 3.17 Figure decrease. both efficiency relationship. the and illustrates power output limits, design tube. vacuum of the limits design the beyond increased is frequency operating the as amplifier C class a of Performance FIGURE 3.17 and D. Fink, (After tube. vacuum (eds.), gridded D. Christiansen a of capability power output wave Continuous FIGURE 3.16 Transit time typically is not a problem for power grid tubes operating operating tubes grid power for problem a not is typically time Transit Power output (W) 1.2E3 1.4E3 1E3 200 400 600 800 MHz and above without serious consideration of transit-time effects. effects. transit-time of consideration serious withoutabove and MHz

0 Power output (W) 1E3 1E4 1E5 1E6 1E7 100 50 0 MHz. Depending on the application, on the used be Depending can MHz. power tubes grid 10 1 10 Electronics Engineers’ Handbook Engineers’ Electronics 100 20 Fr e 30 quenc 200 y (MHz) 50 Fr e quenc 100 300 y (MHz) , 3rd edn., New McGraw-Hill, York, 1989.) Power VacuumPower Tubes Handbook 200 400 300 tput Ou tput (amplier Ou Input 500 (o 1E3 scill ator) ) Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 negligible fraction of the waveform cycle, the following complications are are complications following the cycle, waveform a not the is of fraction electrons at negligible the out of time carried transit are the that operations high amplifier sufficiently frequencies similar or B, class C, class When Transit-Time 3.4.1 Vacuum Tube Principles trated in illus as times, longesttransithave the will pulse the of end and middle the firstsegment ofthe have will pulse the shortesttransit time, thosewhile near the during distance traversing the general, electrons In increased. is quency fre operating the as differ will pulse current the of end and middle, ning, begin the at electrons for times transit resulting the that reveals C amplifier class a as operatedpentode or tetrode, triode, a in anode the to cathode without amplification. tube of the outputthe circuits to controlgrid the from directly simply is transferred stream electron the to To the extent is the case, supplied the energy that this by the exciting voltage tube. the in output useful as appear favorableconditions, may, under it of percentage considerable a fact, In wasted. all necessarily not of is portion energy This the tube. the of anode the at arrive they veloc as the electrons the of affects ity remainder The cathode. acts stream the of this back-heatingof producePart tube. to the in stream electron the to directly ferred tube. the of conditions operationthe within the of bombardment electron of surface. emitting It result also causes the filamentcurrentrequired to a depend upon as cathode the of life the reduce may Back-heatingoperation. normal for required heating cathode total the of fraction considerable supply a fre to sufficient high is back-heating very this quencies,At cathode. the heat to act electrons returning These cycle. the of portion cutoff the space during grid-cathode the in existing field tive thus nega the bycathode the to returned spaceare electrons interelectrode the in trapped the of fraction considerable A operation. low-frequency of case the in off cut be would pulse current plate the instant the at transit in be to electrons of appreciable number an cause to great sufficiently is space Back heating of the cathodewhenthe grid-cathode in time occurs the transit vacuum tubes: grid-based in observed An examination of the total time required by electrons to travel from the the fromtravel to electrons by required time total the of examination An trans is loading input of result a as grid control the by absorbed Energy • • • • applied control to grid the the plate between and the exciting voltage differences current Phase of plate pulses current Debunching current dc grid a produce to grid the reach necessarily not do that electrons to transferred energy of result a as circuit grid control the of Loading heatingBack Figure 3.18Figure of the cathode of the

. The first electrons in the pulse have the time pulse transit in short a electrons first The . Effects 93 ------Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 94 function of time (triode case), (c) electron position as a function of time (tetrode case), and and case), (tetrode time of function a as case). (triode (d) plate current position electron a (c) case),as (triode position time electron (b) of voltage, grid function control (a) amplifier: C class a in effects Transit-time FIGURE 3.18 ) (b (a) (c) (d) Current Distance Distance Time T T Time ime ime Corresp Ac tu Power VacuumPower Tubes Handbook onding pulse at low fre low at pulse onding al pulse al Grid bi as Ca Control Ano Ca Control Sc Ano Pulse tail Pulse re e thod e thod de de en gr quencie gr gr id id id s Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 ode late in the current pulse (those just able to escape being trapped in the the in trapped being escape to ablejust (those pulse current the in late ode less rapidly in the grid-plate space. Finally, those electrons that leaveconsequently, and, the cathtravel minimum the near or at with platepotential plate instantaneous the approach pulse the of middle the near Electrons value. minimum itsatapproachplateplatethey is because the before the potential Vacuum Tube Principles A watercooling system, although more complicated, moreis effective 50 below levels powerair than at common are vapor. water, Air-cooled tubes or coolingair,used:methodof the isfactorseparates thattypesmain tube The Device 3.5.1 of items, list including alaundry must examine engineers design The modeling. and involvescomputer-aidedcalculations that process lengthy a is tube powernew a of be design The mustlife. operating longprovide and reliable tube the all, Above properties. gain/bandwidth high and ciency effi operating high being usually parameters, operating most the important of number a meet to designed be may tube vacuum power particular Any Vacuum 3.5 frequencies, because a longer plate plate current pulse increases losses. atlowa frequency. efficiencyamplifiercausesthe the of drop This to high at operationitwouldlonger plateof in be to pulse bethan current the cause to is effect net The time. transit large havea so and grid, approach the they as towardcathode)slowedcontrolbe the grid-cathode returned space will and • • • stability of the internal elements, and the effects of thermal cycling. of thermal elements, effects the and internal of the stability long-term the construction, in used materials of types the tube, within the elements among expected. variations be spacing can includes that analysis tolerances This manufacturing the and be, will parameters Operational power tube. of the expected gain the including anode, the to cathode the from paths their in electrons the to pens must made be analysis of what hap A careful performance. desired Electro-optics fins. theand spacing of have, thickness thewill the deviceand fins of number the cooled,water or cooled air be will tube the whether include questions Design applications. typical not in will life itlong provide if value little of is tube high-performance A operation. Cooling : how the tube will dissipate heat generated during normal normal during generated heat dissipate will tube the how :

Cooling

Tube : how the internal elements line up to achieve the the achieve to up line elements internal the how :

Design : what the typical interelectrode capacitances interelectrode typical the what :

kW. - 95 - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 96 leaving the tube must be limited to 70°C 1 to prevent the possibility of spot boiling. manufacturers.specifiedtube iscally by Circulating removewater can about maintained.resistivitypuritydegreemustofbeA 1 of in anode, illustrated the as of surface the over flow to water cooling the force jacket, cylindrical a with 50 about powerfor aboveoutputs cooling over air preferred is Waterusually cooling Water Cooling 3.5.1.2 the maintain same cooling effectiveness, increased airflow mustbe provided. As altitude the increases, density (and cooling capability) of air decreases. To movement. to air agiven resistance in resulting manufacturer, the by established its is equipment the not volume.appropriatewithin mass, rate An airflow its of function a is air of capability cooling The volume. flow systemfordevice air-cooled relatedperformance an is notto necessarily air A typical air cooling system for a is transmitter shown in Air Cooling 3.5.1.1 shows how the choice of cooling method is related to anode mustdissipation. be taken into consideration in the selectionexternal blowers,of a fans,ducts,cooling plumbing, heatmethod.exchangers, otherhardwareandFigure 3.19 given water flowand agiven power dissipation.cientmethodcoolingpowerof a amplifierNaturally, (PA) than water tube the cooling, a for complexity ofthe anodekeepthetosufficiently cool. Vapor cooling provides evenan more effi cally move enough air through the device (if the tube is to becooling of reasonableat the 100 size) cooling—byafactor of 5–10 or more—in transferring heat from the device. Air (eds.), Relationship between anode dissipation and cooling method. (After Fink, D. and D. Christiansen FIGURE 3.19

kW/cm Con Because the water is in contact with the outer surface of the anode, a high anode,aouter thesurfacecontact ofthe with in water isBecausethe design. system cooling considerationin a also operationis of altitude The ve Electronics Engineers’ Handbook ction ction 2 kW. Multiple grooves on the outside of the anode, in conjunction conjunction in anode, the of outside the on grooves kW.Multiple of effective internal anode area. Inpractice, the temperature of water He co at sink oling

kW level is virtually impossible because it is difficult to physi

Cooling method 10 1 Figure 3.21Figure , 3rd edn., McGraw-Hill, New York, 1989.) Ra te 100 d ano de dissipation . 10E3 10E4 Power VacuumPower Tubes Handbook (W 106 105 )

m Figure Figure 3.20 Ω cm (atcm25°C) typi Forc Wa Va r co po ter co air ed . Cooling oling oling - - - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 Vacuum Tube Principles and Feeding of Power Grid Tubes Grid FeedingPower of and Staff, Laboratory flow. water (After controlled for grooves with anode Water-cooled FIGURE 3.21 PA system. cooling stage Typical transmitter FIGURE 3.20 , Varian Eimac, San Carlos, CA, Carlos, 1984.) San Eimac, , Varian P A enclosure Co P Exhaust chimne Exhaust A compar A oling airow oling blower tmen y t The Care Care The 97 Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 10 1 to where it is cooled to 30°C–40°C before being pumped back to the tube. 98 Tubes Staff, Laboratory (After system. Typicalcooling vapor-phase FIGURE 3.22 multiple with PAtransmitter shown in is tubes a for system cooling vapor-phase A maintenance. and safety provide operating for to system the in included are interlocks and valves Electric the cycle. completing boiler, the to returned is then condensate The a state. to liquid reverts and energy its The vapor.up gives it steam where condenser, to a waterto passes the vapor converting point, boiling the to water the heats dissipation anode tube, the to applied is powerwater. When distilled with filled boiler a in immersed is anode designed specially a incorporating tube may be increased significantly (all other considerations beingthe same). Viewed from another perspective, for the same watercoolingcapacity watersamegreatlycooling, asflow, butwithreduced water flow. the dissipation ofthe vapor-phaseessentiallythe permitssystema coolingThus, cal. 540requires 30 ingwater. Increasing the temperature of 1 ing [4]. The benefits of vapor-phase cooling arethe result ofthe physicsboilingpoint, theof highergivingboilcoolingefficiency compared with water cool Vapor cooling allows the permissible output temperature of the water to rise to Vapor-Phase Cooling 3.5.1.3 seldom are required. high this dissipations tions, (steam) tube 500 from ranges dissipation the tubes, water-cooled modern typical In After leaving the anode, the heated water is passed through a heat exchanger A typical vapor-phase cooling system is shown in Figure 3.22. A tube tube A 3.22. Figure in shown is system cooling vapor-phase typical A

kW/cm calof energy. However, transforming 1 Insulator , Varian Eimac, San Carlos, CA, Carlos, 1984.) San Eimac, , Varian kW/cm 2 and above. and However, applicascience” “bigofexception the with 2 . Water-cooled anodes have been designed that can operate at operate can that designed been have anodes Water-cooled . Ste Pressure am pressure interl (steam water) (steam Condenser ualizer fitting eq iler Bo Equalizer line oc k

Insulator tu gof water at 100°C into steam vapor

gof water from 40° to 70°C requires Power VacuumPower Tubes Handbook Figure 3.23Figure The Care and Feeding of Power Grid FeedingGrid and Care of Power The (waterbe Vent Wa le Control ve Low wateralarm/interlo ter l Reser ) . bo voir S x olenoid valve ck W - - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 Vacuum Tube Principles of performance and economics. and of performance however,reasons forpreferred are materials of combinations Certain tube. The characteristics of the three emitting surfaces are in summarized totolerant more are they applicationsbecause tube power thoriated-tungsten The tungsten-impregnatedand cathodespreferred in are heater conduction and the tion element. from radia byheated is and outside surface its on material electron-emitting the carries sleeve The sleeve. metal a in (heater) enclosed filament a of consists heated cathode, indirectly An or sagecurrent. heather cathode, ofelectric an pas the by heated wire a is cathode, filament orcathode, heated directly A emission from heat. The cathode may be heateddirectly orheated. indirectly objective. physical to this element Each shock. critical withstand is and temperatures operateto athigh ability the include tube successful a for requirements The elements. internal the of construction and design of racy accu the by determined is tube vacuum any of performance ultimate The Cathode 3.5.2 as sulfurhexafluoride)are usedsometimes to cooltheanode of a powertube. pipes, refrigerants, and, where high-voltage hold-off is a problem, gases (such overloading, requiring special considerations with regard to cooling. Oil, heat applicationsPowertransientfordesigned research formust be devices used Applications Special 3.5.1.4 (After supply. water common a using Staff, Laboratory transmitter 4-tube a for system cooling Vapor-phase FIGURE 3.23 A variety of materials may be used as a source of electrons in a vacuum a in electrons of source a as used be may materials of variety A are most used commonly surfaces of emitting types three The The cathode a in used forpower the required energy electron obtains tube • • • Tungsten-barium-aluminate-impregnated emitters oxides Alkaline-earth tungsten Thoriated The Care and Feeding of Power Grid Tubes Grid Feeding Power of and Care The

Assembly Insulator tu (steam) be St Pressure eam pr eam steam air/water , Varian Eimac, San Carlos, CA, Carlos, 1984.) San Eimac, , Varian ttinfi C B essure interl ondense oiler ualize eq Equalizer line g r: r Insulator tu oc k ion bombardmention (waterbe Wa Vent le ve alarm/interl Control ter l Low wa Low Rese ) S oir rv bo olenoid valv olenoid Table 3.5 ter x oc k 99 e - - - . . Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 100 The life of the tube under such operation, however, is shortened significantly. An oxide cathode that is overheated produces little, if any,desired heateradditionalthe at voltage. emission.limited emission notIn the isfield, still the butpossible heater as coolvoltage as must runs notthat exceedthe design value. high-efficiency cathodea of meansstagedesign bythe in minimized be can bariumtomigratefree device.ing the toother evaporationwithin areas This from bombardment particles. high-energy to subjected when rapidly more deteriorate also and emitters other “poisoned”than or damaged easily more are emitters Oxide drawbacks. their without not are they type, other any than power heating oxide device shown in is cathode. Atypical 20 to up of Tableemission 3.5, in peak shown As advantages Other cathode. low and for emission short temperature. operating pulses peak include high oxide the of advantages main the of one is ity 100–500 of density emission age electrons. be to said then is cathode oxides.The to reduced are subsequently carbonates away, the burned is binder the As temperatures. 40% and carbonate barium carbonate. 60% strontium approximately is mixture The material. a binder in suspended carbonates, strontium and of barium a mixture with temperatures. disk) or can elevated (a at structure nickel a coating toughness first by formed and is layer oxide The is strength alloys retain nickel to of ability property their important most The steels. many and Nickel alloys [4]. nonferrous nickel most as than harder such and tougher, stronger, are metal general, in base alloys, a on oxides of strontium coating and a of barium consists cathode oxide production-type conventional The Oxide Cathode 3.5.2.1 The oxideThe cathode evaporatematerial will tube,ofthelifecaus during the of watt per emission peak more provide emitters oxide-coated Although aver an capableof is 700°C–820°C and at CW operates cathode oxide An are elements these tube, the of processing vacuum During a Source: Impregnated Thoriated tungsten Oxide Emitter Emitters Thermonic of Common Characteristics TABLE tungsten Directly heatedrefers toafilament-typecathode.

3.5 fe Fn, . n D Crsine (eds.), Christiansen D. and D. Fink, After 3rd edn., McGraw-Hill,New York, 1989. Direct and indirect Direct Direct and indirect Heating Method mA/cm a Temp. (°C) Operating 1600–1800 900–1175 700–820 2 Hg eiso cret capabil current emission High . Figure 3.24Figure Power VacuumPower Tubes Handbook lcrnc Egnes Handbook Engineers’ Electronics A/cm Emission Density (A/cm activated 0.04–0.43 0.10–0.50 . 0.5–8.0 2 2 is possible from an an from possible is ) Average and will emit emit will and baked 0.04–10 0.10–20 at high high at 0.5–12 Peak , - - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 Vacuum Tube Principles the carbon has evaporated or has combined with residual gas, depleting depleting gas, residual with combined has or evaporated has carbon the platebombardment, higher so voltages safely applied. be can voltage must be A limited. cathodethoriated-tungsten is more tolerant of ion platebombardment,ion by deterioration caused to susceptible are cathodes oxide voltages.Because higher at plate the operate to ability the is cathode upranges to 10 40–430 of averagean emission produce will filament ventional cathode. ofemission in The result approximately is increase an 1000over times a con envelope, broughtis thorium towire. surface metallic ofthe the filament the tube the of pumping vacuum during processing proper By thoria. of form about 1.5%, the typically concentrationis in thorium The wire. tungsten ing cathode element(s). the of mak process the in added is tungsten to Thorium atmosphere toproduce gaseous layera of filament in exploited is form wire in applications. tungsten of iron-based resistivity or The platinum, alloys. nickel, of conductivity the than copper, better of much that but one-third approximately is tungsten of elec conductivity The trical metal. other melting any of The that 3500°F. than 6170°F, is higher than tungsten more of point of any than temperatures at stronger metal is Tungsten common [4]. emitter other tubes atomic-film grid power of in form used another commonly is filament thoriated-tungsten The Thoriated-Tungsten Cathode 3.5.2.2 The end of useful life for a thoriated-tungsten tube occurs when most of most when occurs tube a thoriated-tungsten for life of useful end The oxide an over cathode thoriated-tungsten a of advantages the of One At operating temperature ofa typical 1600°C–1800°C, a thoriated-tungsten The thoriated-tungsten filament (orcathode) is created in a A/cm 2 or more. Varian, Palo Alto,Varian, CA.) of (Courtesy cathode. oxide typical a of Photo FIGURE 3.24 ditungstencarbide mA/cm high-temperature ­high-temperature on the surface of surface the on 2 . Peak current current Peak . 101 - - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 carbon loss. This cycle works in reverse, too. For a small decrease in in decrease the small layer—hence, a carbide the For of life of too. the because reverse, emission, peak life in and tube works temperature in cycle decrease This 50% loss. a and carbon emission, 20% peak a in temperature, volt cathode in filament increase increase in (K) Kelvin 20 increase a in 3% result a will age Theoretically, layer. surface carbide the 102 Alto, CA.) Palo of Varian, (Courtesy filament. tungsten Spiral-type FIGURE 3.25 mesh A expansion. thermal for compensate to loading spring with ament fil bar-type a dictate considerations mechanical increases, tube the of size the As tubes. low-power in extensively used is filament spiral The design. and filament, spiral-type a shows 3.25 Figure Power tube filamentscan be assembled in several different configurations [4]. Cathode Construction 3.5.2.4 residual the gas. by with of aresult collision ionization as tubes uum emission suffering without ions positiveimpairment. These ions are always present numbers in small in vac positive high-energy by bombardment up ranges to 12mance cath of types (500 section this in odes discussed three the of density emission average highest the provides 900°C–1175°Cat operates and typically cathode tungsten-impregnated The Tungsten-Impregnated Cathode 3.5.2.3 increased. be tube—may Tungsten, as an element, is better able than other emitters to withstand withstand to emitters other than able better is element, an as Tungsten, A/cm 2 . mA/cm 2 –8 Power VacuumPower Tubes Handbook A/cm Figure 3.26 Figure 2 ) [4]. Peak power perfor shows a bar-type bar-type a shows - - - - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 Vacuum Tube Principles A mesh cathode is shown in Figure 3.27. Figure A meshcathode shown in is parameters: vibration. and shock to from damage subject less and designs other than rugged more is It tubes. large and small both for used be can filament The rigidity of a cylindrical mesh cathode is determined by the following the by determined is cathode mesh cylindrical a of rigidity The • • • The ratioThe of welded crossings wire to total cathodethe forming of number,wires The the length and thickness, cathode of the diameter The Mesh tungsten filament. (Courtesy of Varian, Palo Varian, of Alto, CA.) (Courtesy filament. tungsten Mesh FIGURE 3.27 Alto, CA.) filament. Paloof (Courtesy Varian, tungsten Bar-type FIGURE 3.26 103 Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 in the grid structures. In the case of the control grid, less driving power is is power driving less grid, control the of case the In structures. grid the in dissipated is power less interception, grid reduced With of interception. minimum grid a with controlled be to and flow to current plate of amounts large allows construction This centerline. a around cylinder a in arranged 104 ring at the top and to a base cone at the bottom. The lower end of the the of metal end ring, lower the of The construction bottom. The the ring. at contact a to metal cone bonded a is base to assembly a to fastened and are top the supports at vertical ring of number A construction. of of that copper.half almost and iron of that times three than more is molybdenum of ductivity con thermal 1600°F–3000°F.of The temperatures at metals refractory all of suitable most the considered is generallymolybdenum pure basis, strength num, in shown as points, intersecting at wires the weld spot[4]. operators grid The assem the wind using blies that operators by prepared are grids wire Conventional Wire Grids 3.5.3.1 elevated at spacing and vibration. and shock must withstand also They temperatures. shape their maintain must tube power a of tures power levels, laser-cut medium-power most (5–25 For tubes required. the frequency by principally operating determined and is level tube power power a for used grid of type The Grid 3.5.3 value maximum a style of and emitter.to type by the determined zero from ranging well, as vary will emission of ity the energy of the different within emitter electrons is not the same, the veloc electron the byjust before emission and the energy that must be possessed given up to energy escape. Because kinetic the between difference the sents repre that velocity a with depart cathode hot a from emitted electrons The Velocity of Emission 3.5.2.5 high-level modulationlower AM critical circuits. in distortion offer usually basket-weavearrangement a mesh in built example,filaments whole.a as system For RF ofthe that and tube ofthe performance the affect tube. for the required Most power grid tubes are designed as a series of electron gun structures structures gun electron of series a as designed are tubes powerMost grid Grids for higher-power tubes typically are built using a bar-cage type type bar-cage a using built are typically tubes higher-power for Grids may assembly filament the of construction the applications, certain In Figure 3.28 Figure which exhibit stable exhibit which physical at properties elevated a temperatures. On

mandrels kWAt dissipation)common. higher is welded-wire construction Structures . Most grids of this type are made with tungsten or tungsten with made are type this of grids Most . (forms) that include the required outline of the finished finished ofthe outline (forms) required includethe that pyrolytic graphitepyrolytic grids may be found. The grid struc grid The found. be may grids Power VacuumPower Tubes Handbook molybde ------Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 Vacuum Tube Principles hotter the grid, the greater the emissions will be. will emissions the greater the grid, the hotter A grid with contaminated barium become will surface.another emitting The The rategrids. of evaporation of is cathodea function temperature and time. find its wayscreen andand the controlmaterial cathodeto coating the from oxide of an cathode, case device.the however, In may evaporate barium free emission. compounds to reduce primary etary propri with coated are molybdenum or thoriated-tungsten tungsten with of made tubes grids cathodes, In emission. grid reducing in effective are (about550°C).developed coatings applications for high-temperature Special limited however, is plating, gold for temperature operating safe maximum The deposition.by caused emission primary reducegoldto with coated are evaporates surface. grid the that contaminating cathode from the from material prevent to impossible is it though even tube, the of life the throughout ensured be must affinity electron high emission, grid low.however,To be prevent mustemissions, secondary and primary Their additional heat. create grid the in flowing currents capacitive high-frequency Furthermore, heat. into energy kinetic its of part converting beam, electron the also intercepts It cathode. the by radiated heat the of proportion high a absorbs grid The surface. mechanical its of the characteristics physical the both and on structure the of demands stability severe impose cathode hot the to grid induc lead low resistance. RF low assembly and the tance give base metal cylindrical and cone, base rmr gi eiso i uuly o i a hrae-ugtn cathode thoriated-tungsten a in low usually is emission grid Primary In tubes with oxide cathodes, grids made of ortungsten molybdenum wire The result is that grids are forced to work at temperatures as high as 1500°C. the of proximity the and operation during grid a of loading external The Mesh grid structure. (Courtesy of Varian, Palo Alto, of Varian, CA.) (Courtesy structure. grid Mesh FIGURE 3.28 105 - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 of molybdenum wire doped to prevent brittleness and recrystallization. To recrystallization. and brittleness prevent to doped wire molybdenum of the temperatures) higher (and,therefore,powers higher at operation To permit K-Grid 3.5.3.2 106 Varian, Palo Alto,Varian, CA.)of (Courtesy assembly. completed (b) and processing laser (a)before grid: graphite Pyrolytic FIGURE 3.29 time of amount the to proportional is layer the of a thickness on The form. deposited grid is graphite pyrolytic of layer A environment. controlled a in temperatures high at gas hydrocarbon a of decomposition the by duced processing. laser after and before grid pyrolytic-type typical a shows 3.29 Figure grid. style conventional- computer-a simulate to cup The the in holes numerous dimensions. cuts laser controlled proper the of cup graphite formed a are laser-cutting grids by pyrolytic devices, high-power for primarily Used blies. Pyrolytic grids are a alternative high-performance to orwire bar grid assem Pyrolytic Grid 3.5.3.3 sions to a minimum. The surface structure maintains low secondary emissions. layer of platinum. thin next is coatedcarbide zirconium with (sintered at 2300 at2300 vacuum under stresses, the at grid is annealed mechanical 1800 eliminate yoyi (r retd gaht i a om f rsalzd abn pro carbon crystallized of form a is graphite oriented) (or Pyrolytic Despitetemperatures,gridhigh platinumthe coatingemis keepsprimary K-grid (a) has been developed (Philips). The K-grid is a spot-welded structure K to degas the molybdenum wire. The grid structure structure grid The molybdenum wire. the degas to K 5 1 0 0 2 in. cm ) (b Power VacuumPower Tubes Handbook K) and, finally,with a K. It is then baked - - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 of the grids inside the tube at elevated temperatures. This preserves the the preserves This temperatures. elevated at tube the inside grids the of movementprevents expansion of coefficient small Their metal. like expand depositedof the conditions. graphite depend uponimposed the properties mechanical and depositionallowed is tostructural continue. The Vacuum Tube Principles Screen grid assembly of a typical tetrode PA tetrode tube. of atypical assembly grid Screen FIGURE 3.30 apply,conventions two these tubes, pentode For current. grid minimize to the plate. In a tetrode, the controlmust grids and screen be precisely aligned pathto cathodeelectron the the from totransparent mustgrid be essentially large part, the operating of characteristics the tube. For best performance, the grid screen assembly. typical a of construction the shows 3.30 Figure ring. contact a to bonded is which of end lower the cone, base metal a to fastened is Each cathode. the from viewed as concentric. grid, previous and the than larger cylindrical slightly is Each are grids suppressor and screen, control, The Grid Physical Structure 3.5.3.4 grid the Additionalthat grids. benefitsare wire pyrolytic be maintained, can grids be spaced more closely conventionalthan of the device.characteristics desired electrical tighter Because tolerances can yoyi gis r iel aum ue lmns eas te d not do they because elements tube vacuum ideal are grids Pyrolytic The shape of the control grid and its spacing from the cathode define, in define, cathode the from spacing its and grid control the of shape The • • • Can operate low with Can temperatures vapor at high pressure copper ofnearly that planes three the of two in conductivity thermal a Has no weld having points structure asingle Is C ylindrical metal ba metal ylindrical Figure 3.31Figure se provides acutaway power of view atetrode tube. Base cone Me tal ca tal p C ylindrical scre ylindrical Lower halfofano Sc Ceramic re cont en contact ring act ring act en gr id de 107 Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 108 result is electron flow from screen to flowplate.screen from electron is result The them. attract plate, the and will screen potential anode much the higher the between region the into however,If,element. pass that they to back fall will they screen, the to attraction stronger havea electrons these If emitted. the by intercepted screen grid. As the are the strike electrons screen, other low-energySome plate. are electrons the to way their on screen the through pass electrons all Not cathode. the from emitted electrons the accelerate to surface of application the through treatments. reduced be of may yield The used. electrons cathode of secondary type the of regardless occur may emission second for [4].potential grids Secondary the suppressor and screen, raises control, the from This emission ary physical increases. the also increases, elements tube the a of of size capability power the As design. carefully any considered be in must tube vacuum a of elements other and tures struc grid the to electrons secondary of properties the of relationship The Considerations Emission Secondary 3.5.3.5 beam suppressor for interception the grid. minimum and alignment precise for requirement the to addition in tetrode a of power tube. assemblies cathode and grid, control screen, anode, the of arrangement Internal FIGURE 3.31 In a tetrode, the screen is operated at a relatively low potential, necessary necessary relatively lowpotential, a atoperated is screen the tetrode, a In Sc re en contact ring Grid contact ring Inner heater contact ring Power VacuumPower Tubes Handbook ter he Ou Inside surface of surface Inside ano Sc Control sembly de as ter he Ou re Inner heater en gr Ceramic ater cont gr id ater id act ring act sembly as sembl as y - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 reverse electron flow onthe screen element, a conditionmoreelectrons leave commonwill arrive.willscreen thegridthan result Thetoa be will high-power electrons. During a portion of the operating cycle of thecontrolno virtually over device,screen-to-plate result secondary current flowita of as is possible that Vacuum Tube Principles Series power supply configuration for swamping the screen circuit of a tetrode. (After (After tetrode. a of circuit screen the swamping for Staff, Laboratory configuration supply power Series FIGURE 3.33 Tubes Grid FeedingPower of and Care supplyStaff, Laboratory for (After screen a a tetrode. low-impedance for providing Circuit FIGURE 3.32 tron flow,the screen voltage will attempt torise to the plate voltage. Note the of reverse elec powerdirection supplythe excessively is in impedance high current. Two emission common the approaches are counteract illustrated in Figures 3.32to supply and power3.33. If the screen screen the from current tetrodes. A low-impedance path for reverse electron flow must be provided. Becausephysicaltheof constructiontetrode, aof controlhavethe will grid Tube manufacturers typically specify the recommended value recommended the of bleeding specify Tube typically manufacturers E c1 90V The Care and Feeding of Power Grid Tubes Grid FeedingPower of and Care The + – E c1 – + , Varian Eimac, San Carlos, CA, Carlos, 1984.) San Eimac, , Varian E c2 400V – + 25 kΩ 4 mA , Varian Eimac, San Carlos, CA, Carlos, 1984.) San Eimac, , Varian 12.5 kΩ 24 mA – + E E c2 b – – + + E b 2k – + V 109 The The - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 screen voltage rises, the secondary and plate currents will increase, and the the and increase, will platecurrents and secondary voltagethe rises, screen the As element. pass series regulator the in cathode to anode from flow to try will electrons reverse the bled, well not is supply the If only. direction flow electron forward the Most in impedance direction. low are flow supplies power electron regulated reverse the in impedance low on emphasis 110 resent only a small percentage of the total load the driver works into. driver so that changes in the load resulting from secondary grid emission rep toleratetoas manner a condition. this techniqueinvolvesOne swamping the stage that works into such a nonlinear load normally must be designed in suchpotentialcontrol highattractemittedtheelectronstofrom thegrid. A driver such as the anode in a triode or the screen grid in a tetrode—is at a sufficiently decreasing grid current with increasing grid voltage when another electrode— with 200–600 secondary emission is concerned. Any power grid tube that normally operates chart will show the region between 200 the and 600 of examination An potential.electron primary of function a as given is a curve form in emission characteristics of the metals used in the grid structure. secondary normal the byexplained be can current grid reversalof and tion eventuallyreverseatakes voltagegrid the direction as reducincreases. This in shown is ofvoltagegridfunction forhigh-powera thoriated-tungsten filament tetrode triode,a in occurcan tetrode, or pentode. typicalAcurveof gridcurrent a as thoriated-tungstencathodewhethera existtheis can oxide or emitter, itand ary emission from the control grid can occur. Control grid secondary emission cal potential. As this geometry increases in electrical terms, significant second life. tube with increase cathode tube,will impedance is excessively grid high. emission, Primary in the case of an oxide circuit grid the if problems operational in result can emission grid Primary general characteristics. same the of tetrode a for than higher somewhat however,pentode, be may fora power supply.requirement grid current screen forthe path screen The flow electron reverse a provide to requirement the reducing device, the in The plate-to-cathode voltage is then the sum of the potential. ground dc at operated is screen the where circuits in extensively used is scheme This currents. plate and screen normal the obviously, carry powersupply,supply. powersupply screen must,screen the swamping The of circuit the (20shown). In emission grid screen for path a provides ground to enter arunaway condition. will tube The secondaryThe emission characteristics ofcommon metalspresentedare in The size and power of gridded tubes dictate certain characteristics of electri circuit. control ofgrid the must impedance consider the also designer The The suppressor grid of a pentode of the emission effects lessens secondary in shown As Figure 3.34Figure

V on the grid can exhibit the negative resistance characteristic of Figure 3.35 iue 3.32 Figure . As shown in the figure, grid current decreases and decreases current grid figure, the in shown As . Figure 3.33 Figure . The ratio of secondary-to-primary electron current te diin f 12.5 a of addition the , , plate current flows through the screen screen the through flows current plate , Power VacuumPower Tubes Handbook

V to be rather critical as far as E k b and Ω resistor from screen screen from resistor E mA for the circuit circuit the for mA c 2 power supplies. - - - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 Vacuum Tube Principles purpose because it has the highest electrical conductivity of any metal metal any of conductivity electrical highest the has it because purpose this for material excellent an is It anode. the construct to used Copper [4]. is generally specifications tight to assembled and machined are that parts of smaller many a collection of plate The a assembly is typically power tube Plate 3.5.4 (After conditions. ordinary under metals various of Staff, Laboratory characteristics emission Secondary FIGURE 3.35 CA, Carlos, 1984.) San Eimac, Varian Staff, Laboratory (After tetrode. filament tungsten thoriated- high-power a for voltage grid control of function a as current grid of curve Typical FIGURE 3.34

Coefficient of total secondary radiation 0.5 1.0 1.5 2.0 0 0

200 Assembly –5

Grid10 current15 (A) 20 25 30 The Care and Feeding of Power Grid Tubes Grid FeedingPower of and Care The 0 5 0 400 250 Primar 600 Carb on black on nicke y impact ener impact y 800 500 Grid 1E3 tentipo 750 (V gy 1.2E3 l h Cr ad edn o Pwr rd Tubes Grid Power of Feeding and Care The ) al (V 1.4E3 , Varian Eimac, San Carlos, CA, Carlos, 1984.) San Eimac, , Varian 1E3 ) 1.6E3 1.25E3 1.8E3 1.5E3 Moly Nickel Copp enum bd er 111 , Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 112 of ceramics are in common usage in the production the of vacuum usage common in devices: in are of ceramics types Three tubes. powervacuum modern of part integral an are Ceramics Ceramic Elements 3.5.4.1 envelope the as ceramic material. use devices that with however,replaced, been have Most tubes. power older in used were lopes toouter vacuum,the itexternal surface is be cooled can directly. enveGlass 3.36.Figure in shown two as complete unit, a form to weldedthe assembly,together are ring of the of halves time the At spacer. ceramic base a to bonded is ring contact anode the of half lower assembly. The the of outside the to welded silver-soldered or fins cooling and mouth the weldedto ring platecontact a furnace. abrazing one into piecebrazed in and clamped, positions, proper their in stacked are fins cooling and anode the machined, been have parts the of all After shapes. and sizes thenecessary into manufacturer tube the by stamped are They copper. of sheets flat and bending, drawing, deep as stamping. ideally such and operations fabricated cold-forming easily to is suited copper Furthermore, silver. pure except tube. power amplifier RF of an structure Cutaway anode of the view FIGURE 3.36 In most power tubes, the anode is a part of the envelope and, because the the envelope because and,the of part a is anode the power mosttubes, In of half upper the with cup copper a resembles tube power a of plate The as begin device) air-cooled an of case the (in fins cooling and anode The • • • Aluminum nitride Beryllium oxide Aluminum oxide (BeO)-based ceramics -based ceramics -based (AlNi)-based ceramics e Anod Ceramic Power VacuumPower Tubes Handbook ano Lower halfof Upr halfof pe cont de contac ring act ring act Co sembly as

oling fi oling t n - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 lmnm xd i 2 tms ihr n hra cnutvt ta most than conductivity thermal in higher times 20 is oxide construction Aluminum common a are components,vacuumtubes. including ofelectric widevariety fora material insulators ceramic oxide-based Aluminum Oxide Aluminum Ceramics 3.5.4.2 Vacuum Tube Principles greater efficiency in design in modification. design efficiency greater for is allow can vendor. often This ceramic fabricator,the device not process the byapplied the that is metallization thick-film of advantage Another thick-film for reversed are attributes These films. resulting the of resistivity high the is disadvantage The cost. moderate their is tungsten or advantage of the high-temperature schemes metallization with molybdenum paste. and palladium, thick-film the in incorporated is platinum, usually phase silver, A glassy combinations. gold,their as such used, are metals Precious atatmospheres formed in oxidizing moderate (800°C–1000°C).temperatures both. or copper, nickel, with 1500°C. above plated electrochemically is usually metallization temperatures resulting The at atmospheres moist and reducing in slightly firing by accomplished is This the bonding. or proper phase for phase glassy glassy added internal an requires metallization of mechanism The of slurry a with powder may powder.glass be added metal to the of alumina, the purity the coated been has on powder. it Based metal powdertungsten or after manganese and molybdenum article formed the refiring postmetallized by are usually aluminas shaped Fired, processing. thick-film or firing high-temperature either by accomplished is ally accomplished is usu of aluminas this Metallization which technique. the processing dictate by frequently means The metals. to bonded being from (2 finishes smooth of finish surface 3–25 The typically is casting. aluminas tape or casting slip for slurries or in extruded, prepared be pressed, may powders the application, final the on Based and 1600°C. 1500°C between to temperatures densification the reduce tives centages of per various with powdersoxide aluminum from fabricated are Aluminas however, ceramics, including drawbacks, of alumina use to the are There ceramics. oxide most of that than greater times four two to is ceramics high-alumina commercial of strength flexure oxides. The Each approach to metallization has advantages and disadvantages. The The disadvantages. and advantages has metallization to approach Each per been has traditionally ceramics alumina of processing Thick-film apart used rarely are applications tube vacuum for ceramics Alumina • • Moderately high dielectric constant (approximatelyModerately constant dielectric high 10) BeO as such materials, ceramic to other pared (approximately 7 expansion thermal Relativelyhigh sintering promoters μ m/in.), may surfaces lapped be or the polished. μ m/in. as a result of normal processing. For very For processing. normal of result m/in.a as , which produce the glassy phase ppm/°C),com low-temperature ­low-temperature . The later addi materials. ­materials. - 113 - - - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 ... Beryllium Oxide Ceramics 3.5.4.3 of choice. ceramic the is 114 Thermal conductivity of common ceramics. of common conductivity Thermal FIGURE 3.37 ity of AlNi is comparable to that of BeO but deteriorates less with temperature.cerns of BeO-based materials. As shown in Figure 3.37, the thermal conductiv AlNi-based ceramics have been developed as an alternative to the toxicity con Ceramics Other 3.5.4.4 appliedoften device by fabricator. the are and precautions safety elaborate less necessitate usually coatings Such substrates. BeO to applied be special may with systems vendors thick-film by Reliable equipment. handled are also postmetallization and drilling, cutting, Simplesafely. them handle to equipped laboratories in processed be they that powdersmandate the of properties toxic the although pounds, It is, however,mina. slightly lower also strength. in has a lower constant dielectric and coefficient ofaluthanthermal expansion illustrates, BeO chart the some As alternative and materials. ofthat alumina conductivity with of 3.37 BeO Figure materials. thermal comparesbased the alumina- of that than higher approximately 10 is times BeO of conductivitythermal The properties. chemical and physical, electrical, their of because designs. tube many handled in successfully be used been has mustBeO properly.safeguards, necessary and Withthe hazardous potentially are that materials of group a The major drawback is the toxicity of BeO. and its compoundsBeryllium are ceramics. waysalumina-based superiortomany in are ceramics BeO-based In tubes designed for operation at 100at operation for designed tubes In Beryllia materials are fabricated in much the same way as alumina com alumina as way same the much in fabricated are materials Beryllia tubes vacuum power in use for attractive particularly are materials BeO

ermal 100 conductivity150 200 W/m ( 250 K) 300 50 0 50 0 100 B 150 eO Temp 200 erature ( SiC 250 300 ° C) MHz and below, alumina typically typically below, and alumina MHz 350 Power VacuumPower Tubes Handbook 400 450 500 Al 170 AIN AIN 200 AIN 2 O 3 - - - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 con carbide (SiC)-based ceramics. boron nitride and substances but its thermal expansion is low (4 The dielectric constant of AlNi is comparable to that of alumina (a drawback), Vacuum Tube Principles 200 miles above earth. 200 miles the of mercury). outer degree vacuum the in is space For about this comparison, 10 and must be driven out for long component life. A vacuumtypical reading of copper is used in some tube construction, residual oxygen in exists the metal assembly. the of Although parts copper the from gases other or cedure. Baking stations are used to evacuate the tube and bake out any oxygen tube is brazed into a single unit. The device then goes through a by changes. temperature stressed whenbreak mechanically to ceramic the cause can damaging, themselves ceramic, not in the in cracks smallest The failure. of cause potential a is envelope, brittleness tube a their not completed compromised. be that so used bonds will are temperatures highest-temperaturethe stagestheassembly As form,first. takes lower oven suitable for brazing. surface a provides and ceramic the to bonded molecularly is that structure preparation in a high-temperature oven, the painted area provides a metallic mate a is that using rial created are seals ceramic-to-metal The tube. the of base the form to one previous the upon builds element each sections, in Assembled unit. tobase produce afinished as to referred sometimes (aatmosphere oxygen-free process The base subassembly is welded using a parts: two essentially in built most devices.is Avacuum tube to however, common is construction, physical basic The concerned. are tics characteris operating its as insofar unique is tube powergrid of type Each Tube 3.6 Other Other ceramic materials that findsome inuse vacuum includedevices sili After the base assembly has been matched with the anode, the completed anode,the the with matched been has assembly base the After Despite all the advantages that make ceramics one of the best insulators for of completion dictate that sequences temperature requires process This The ceramic elements used in a vacuum tube are critical parts of the device. −8 • • Torr is specified for most powertubes (formerlyas expressed 10 machining steps machining The anode, which includes the heat-dissipatingmade infins various suppressor (if and grid, used) grid screen grid, control stem, supporting and filament the includes which base, The

painted Construction onto the ceramic and then heated in a brazing oven. After brazing a heated in then and ceramic onto the

ppm/°C). tungsten-inert gas (TIG) process in an Heliarcwelding bake-out ­oxygen-free −8 mm of pro 115 - - - ) - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 however, will exhibit reduced breakdown voltage because the gas will form form however,will voltagegas reducedbreakdown the exhibit because will gases, absorbed containing electrode An and environment. other surrounding each the to to respect of with elements potentials the high at tube, operate vacuum typically a which of operation reliable for essential is erty 116 is aggravated,is possible. is damage tube and the fingersocket. After a loses connecting its spring action,the will heating effect currents RF of to mayresult concentration, concentration damage this ofextent the on Depending a result. rings, element tube the with contact socket. of atetrode plated to reduce resistance. RF are silver fingers The present at temperatures atterminals. high the tube the made are coppersurfaces of contacting to tension beryllium preserve spring either of spring consist socket the of portions contacting the configurations, surfaces, cylindrical socket possible large are several terminals tube the have If operation. of frequency the upon may depending design tube one Any Tube 3.6.2 improved by silver plating. design providesconnector for operation atConductivity frequencies. is high tube/ concentric The coaxially. grouped be to them allow rings contact ous vari the of diameters different The ceramic. oxide aluminum of that to ble compara is expansion thermal of coefficient whose alloy iron-nickel-cobalt an is Kovar connections. external the for rings contact as serve also which supportcal device. for the cal connectors. The connectors provide a broad contact surface and mechani the to worldoutside inside elements.the Tubes tie are designed to to be mounted vertically on their electri used connectors the on demands stringent power high The levels at and frequencies operatevacuumwhich tubes place Connection 3.6.1 by caused of loss generally is emission. avacuum tube in life titanium. and barium, cerium, include zirconium, getters “get” or trap and hold gases that may exist inside the tube. Materials used for a contain pocket. gas of the breakdown voltagethe vicinity the in lowering and pressure gas surface the increasing surface, electrode the on A vacuum offers excellent electrical insulation characteristics. This prop This characteristics. insulation electrical excellent offers vacuum A If the connecting fingers of a power tube socket fail to provide adequate provide to fail socket tube power a of fingers connecting the If ring-shaped on mounted are typically grids cathodeand The of End process. chemical evolving an is tube vacuum a of operation The ofTo component, the life vacuumthe a high during power maintain tubes collets getter

Sockets or an assembly of spring fingerstock. Usually, these multiple- these Usually, fingerstock. spring of assembly an or device. The name comes from the function of the element: of the to function the comes device. from name The

Points Figure 3.38Figure shows a cutaway view of base the Power VacuumPower Tubes Handbook Kovar bases, - - - - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 Vacuum Tube Principles eration of products. spurious the gen and amplifiers prevents self-oscillation ofvacuumtube putcircuits of Cancellation common offorms these coupling the input between and out neutralized is amplifier met: are when conditions operating two RF An another. to design one from considerably vary end this accomplish to means The applications. most in performance acceptableprovide to neutralized properly be must amplifier power RF An Neutralization 3.7 inductionheating.as such applications,low-frequency for useful is device of type This socket. a for requirement the eliminates configuration a Such tube. the of bottom the on studs via connected are leads filament The chassis. the to bolted is that Intended for cathode-driven service, the grid assembly is formed into a flange points. connection the showing socket of atetrode base of the section Cross FIGURE 3.38 A series of specialized power tubes is available with no sockets at all. all. at sockets no with available is tubes power specialized of series A • • Insulat rode) canceled. is tet a (in assemblies cathode and grid screen the of inductance The cir output canceled. is cuits and input the between capacitance interelectrode The F standof ed ingerst oc k f Soc ke t ba t sepl at e cont Grid Sc filamen re cont ter Ou en contac ac t ac t t t filamen cont Inner Ca vity de vity ac t t ck - - 117 - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 lowing principles also apply to lower frequencies.) The feedback elements feedback The frequencies.) lower to apply also principles lowing fol the [4]. band of (Many VHF the in a operating amplifier ofRF tube vacuum neutralization affect that elements primary the illustrates 3.39 Figure Circuit 3.7.1 118 and Feeding of Power Grid Tubes Grid FeedingPower of and PA Staff, of a tetrode Laboratory (After stage. neutralization the involved in Elements FIGURE 3.39 positive increasing represents above baseline distance the the that mind in Keep point. ground at the established line, above zero potential the plate( The tube. the of grid the on current driving cal voltage( circuit output RF the other. to each respect with positive as treated or negative be orcan out phase and of phase eitherin are therefore, each, by represented voltages The reactances. pure are involved elements circuit the of all that assume illustration, this of purposes the For (zero). ground to respect with circuit the of part each voltagefor RF the of above or below height the the zero potential line represents the that magnitude and polarity so arranged been have figure previous the of elements cuit band. VHF the in operating pentoderode and tubes voltage( developsvoltage a inductance (− screen the through current The inductance. lead screen the and capacitance ( circuit plate the ( tance ( capacitance grid-to-plate residual the include The voltages plotted in the figure represent those generated as a result of result a as generated those represent figure the voltagesin plotted The Figure 3.40 C ps E ), and screen grid lead ( ),grid inductance screen and p ). The − The ). graphically illustrates the electrical properties atgraphically illustrates the electrical work. The cir

Analysis E E p ) causes a current ( current a causes ) potential often is used as a method of neutralizing tet neutralizing of method a as used is often potential , Varian Eimac, San Carlos, CA, Carlos, 1984.) San Eimac, , Varian C C gp gs E p ). No attempt is made to illustrate the typi the illustrate to made is attempt No). E ) with a polarity opposite that of the plate the of opposite that polarity a with ) I ) to flow through the plate-to-screen plate-to-screen the through flow to ) L s Power VacuumPower Tubes Handbook ). The RF energy developed). energy RF The in I C C gp ps L , lt-osre capaci plate-to-screen ), s P –E ) has a high positive high a has ) E p potential. ­potential. The Care Care The - - - - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 Vacuum Tube Principles essary to provide some of form essary stage neutralization. becomes inductances more important. At VHF and above, it is generally nec voltages connection capacitances external and interelectrode bycaused tube tion. However, of stageas gain need the to the the feedback cancel increases, neutraliza without band MF the through operate will generally amplifiers The elementgrounded-grid components. sufficientis to prevent oscillations. spurious Tetrode neutralization external without band VHF the oper into be ated can triode cathode-driven grounded-grid, a speaking, Generally ofA mayvariety a methods vacuumto be amplifier [4]. used neutralize tube Circuit 3.7.2 result as a of filament to the voltage (− ( voltage RF plate of values the for matched ( capacitance to-screen across a divider circuit that consists of the grid-to-plate capacitance and grid- potential and screen lead inductance voltage, − filament at is operates circuit input concerned. the grid on circuit The output the of action baseline. any as zero insofar potential the at rests potential grid tance The effect of the out-of-phase potential developedscreen as a result of induc tetrode a of 1984.)CA, San Carlos, self-neutralization Staff, the Laboratory in (After involved stage. elements RF the of representation Graphical FIGURE 3.40 h ttl F otg bten lt ad cen s ae p f h plate the of up made is screen and plate between voltage RF total The The circuit. neutralized perfectly a constitutes figure the depicted, As L s is shown, resulting in the generation the of in − shown, is resulting E ), the control exhibit grid zero will voltage with difference respect Negative

Po Design sitive

Components of output voltage 0 V C gp and and E h Cr ad edn o Pwr rd Tubes Grid Power of Feeding and Care The p . C gs ). When this potential divider is properly is divider potential this When ). C d Gri C gp gs E p E C ) and screen lead inductance inductance lead screen and ) ps . This . total This voltage is applied Ca L Sc s E e thod re Pl . en at e –E E , Varian Eimac, Eimac, Varian , 119 - - - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 caused by residual plate-to-grid capacitance [4]. This method assumes that that assumes method [4]. capacitanceThis plate-to-grid residual by caused employstypically a capacitance bridge to circuit balance out the RF feedback For operation at frequencies below the VHF band, neutralization for a tetrode Below VHF 3.7.2.1 120 Varian Eimac, San Carlos, CA, Carlos, 1984.) San Eimac, Varian Staff, Laboratory (After neutralization. grid Push–pull FIGURE 3.41 capacitor, neutralizing voltagesThe present. lower the of plate because the in than circuit grid the networkin push–pull a create to simpler usually is It neutralization. proper for voltagenecessary out-of-phaseprovides the that scheme neutralization grid basicpush–pull a using either a push–pull output or push–pull input circuit. cathode-to-plate capacitance PA of the tubes. capacitors have internal neutralizing oppositevaluetothe a The tube. equal capacitors ( in shown as stage, symmetrical out tube. its respective from of each tube. Fine adjustment is accomplished by moving the conductor in or plate the from distance short a spaced is rod) short (orTypically,a wire the positioned to is “look at” wire the plate Each of deck. the tube on the chassis opposite the half of the circuit. through brought and circuit grid each the ofto side connected wire simple a with accomplished in be can shown neutralization cases, as some In devices, used. are capacitors the neutralization Small-value of Figure 3.41. cross-neutralization with accomplished be screening expected the tube. the inside action providing ground, to bypassed well is screen the In In the case of a amplifier,single-ended canbe neutralization accomplished cathode-driven a for used be can neutralization of method similar A can tubes pentode or tetrode push–pull low-power of Neutralization C fp C gp C n ) are connected from the cathode of one tube to the plate cathode to the ofthe one from tube of the connected ) are F 1 C n iue 3.42 Figure G 1 The Care and Feeding The Tubesof Grid Power C . Note that the neutralization neutralization the that Note . G Power VacuumPower Tubes Handbook n 2 , is small and may consist of consist may and small is , tput Ou C n Input P 2 F Figure Figure 3.43 2 C gp shows C fp , Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 Vacuum Tube Principles grid-to-plate capacitance. interelectrode design, a such In neutralization. phase with the grid voltage, and is fed back to the plate through developsacross that ground to ground by a small amount because of the addition of capacitor shownin method the capacitance tube. of the input the to size in equal is generally capacitorpadding The tuning. while with parallel in capacitor padding previously).A (described wire feedthrough simple a Tubes Grid FeedingPower of and Staff, stage. (After Laboratory tetrode a in single-ended neutralization grid Push–pull FIGURE 3.43 Tubes Grid FeedingPower of and Staff, Laboratory (After circuit. for a grounded-grid neutralization stage Symmetrical FIGURE 3.42 Single-ended tetrode and pentode stages also can be neutralized using using neutralized be can also stages pentode and tetrode Single-ended C fp C gp RF in RF C 1 , often is added to maintain the balance of the input circuit circuit input the of balance the maintain to added is often , put Figure 3.44 Figure F , Varian Eimac, San Carlos, CA, Carlos, 1984.) San Eimac, , Varian CA, Carlos, 1984.) San Eimac, , Varian C 1 n –E C c . The input resonant circuit is placed is above circuit input resonant The . C upon the application of RF drive is out of out is drive RF applicationof the upon G n 1 is considerably larger in value than the the than value in considerably larger is G 2 C Input tput Ou 1 C n C RF out RF n To scre P F 2 2 rcci uit put C en C . The voltage n to provide C gp The Care Care The The Care The C fp 121 Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 122 induced in the input by capacitances,tube the internal grid-to-plate ( amount ofthe and stray capacitances in in shown as capacitor, bypass side screen of screen plate the to the the capacitor bypass returned is that in design amplifier RF usual the from differs circuit bridge.This izing slightly above and ground the capacitancesusing tube as part of the neutral circuit plate the taking by neutralized be can also amplifier single-ended A where followingconditionwhen met: the is show the capacitance bridge that makes the design work. Balance is obtained Laboratory (After Staff, neutralization. in involved elements the show to redrawn figure Previous FIGURE 3.45 Tubes Grid Power Staff, Laboratory (After tetrode. a for neutralization grid Single-ended FIGURE 3.44 C C C C to 3.45 Figure in redrawn is circuit neutralization grid single-ended The gf gp n is the input circuit bypass capacitor bypass input the circuit is is the neutralization capacitance neutralization the is The Care and Feeding of Power Grid Tubes Grid Feeding Power of and Care The is the total input capacitance, including tube and stray input and total capacitance, capacitance the tube is including is the grid-to-plate capacitance the is interelectrode RF in RF "A , Varian Eimac, San Carlos, CA, Carlos, 1984.) San Eimac, , Varian C put C n iue 3.46 Figure C C gf gp C C Te ie f cen yas capacitor bypass screen of size The . n , Varian Eimac, San Carlos, CA, Carlos, 1984.) San Eimac, , Varian = C C C gp gf C are chosen to balance the voltages the to balance chosen are

Power VacuumPower Tubes Handbook C n To scre RF out RF en supply To plate The Care and Feeding of of Feeding and Care The RF out RF put H put V C gp ) and (3.12) C - s

Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 Vacuum Tube Principles tion is low enough that inductances in the socket and connecting leads can can leads connecting and socket the in inductances that enoughlow is tion capacitance.grid-to-cathode the and capacitance grid-to-screen the of sum input the primarily tube is capacitance The capacitance. input tube published the is capacitance half approximately screen-to-grid the structures, pentode and tetrode usual In followingcondition when met: the is obtained is form. Balance ( screen-to-grid Staff, Laboratory (After present. bridge capacitance the showing neutralization plate Single-ended FIGURE 3.47 Tubes Staff, Laboratory (After neutralization. plate Single-ended FIGURE 3.46 Note the examplesthat in given, it of that the frequency operais assumed , Varian Eimac, San Carlos, CA, Carlos, 1984.) San Eimac, , Varian The Care and Feeding of Power Grid Tubes Grid FeedingPower of and Care The RF in RF put C sg ). This circuit is redrawn in Figure 3.47 Figure bridge in redrawn is usual the in circuit ). This C C sg gp C C gp sg C C p s , Varian Eimac, San Carlos, CA, Carlos, 1984.) San Eimac, , Varian = C C gp sg

C C p s C C The Care and Feeding of Power Grid Grid Power of Feeding and Care The s p By Input pass By pass +E b RF out RF tput Ou +E put b (3.13) 123 - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 cially in single-ended tetrode and pentode and stages. tetrode single-ended in cially espe considered, be must inductances stray of effects however, the bands, higher below.At and applications MF in true basically is This ignored. be 124 tances of the tubes. the of tances of capaci bridge plate-filament the a to equal is and that used is ground, capacitances to are neutralizing impedance amplifier zero push–pull a having point of a to grids connected the technique, first the In amplifiers. required. is tralization neu when determine frequency operating the and tube the of physicalsize The capacitance. plate-to-filament of result the longerno is to circuit input the output the from feedback The significant. becomes reactance inductive the controlis notneutralization until grid leadGenerally required speaking, circuit. input outputthe to the from capacitiveto shield a currents as serves and ground RF at operated is grid control [4]. The circuit com grid-driven mon more the to alternative attractive an offer amplifiers Grounded-grid Grounded-Grid 3.7.3 adjustable to achieve set neutralization. straps are ground straps.Two connecting additional short six using deck cavity the tobonded is screen application, the grounded-screen this In neutralization. achieve to met for be complete above.tance—must at and stage VHF stability induc lead grid control for compensation and independence circuit output and conditions—input Both circuit. output the cathode-to-grid on the signal of effects the negate the to sufficient itself, by between not, is currents circuits output capacitive and input by coupling of suppression the because required is condition completeforstability. This canceled be must also grid control the of inductance incidental of effects The frequencies. radio at tion opera proper for required equation the of half only is circuits output and result. input modulation of phase the angle impedance, will phase of variations produce stage the voltageof output the in variations If of inputthe independentand output.to tuning ensure Isolation is necessary currents. reactive to respect with other each of independent circuits output can be used to accomplish neutralization in a simple, straightforwardproperly,inductancesmanaged thesemanner. Ifelements. cathode and grid, screen, above, residualthevoltagesinductance RF the significant may developof in vides special challenges and opportunities to prothe frequenciesdesign high engineer.very atoperating At tubes VHF and grid powerofNeutralization Above VHF and 3.7.2.2 Two methods of neutralization commonly are used with grounded-grid grounded-grid with used are commonly neutralization of Twomethods Figure 3.48 input the between independence previously,noted exhibiting As circuit a and input tube the make to required is above, and neutralization AtVHF shows a PA stage employing stray inductance of the screen grid

Amplifier

Neutralization Power VacuumPower Tubes Handbook ------Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 Vacuum Tube Principles which an which appropriatean the grids. Under between is connected reactance these capacitances in ofand tubes, the torsinternal havethe from values differing capaci neutralizing the which in case general more the of forms special as circuits output and capacitances tubes. of the internal the input from resulting between coupling the for compensate will that value a amplifier, of push–pull a of grids the between or ground, and grid layout of cavity. (b) mechanical and (a) diagram deck: cavity schematic the and connector the screen PAthe ofuse between stray through inductance Grounded-screen stage neutralized FIGURE 3.48 Behavior of these two circuits is quite different. They may be considered be may They different. quite is circuits two these of Behavior the between inductance an requires neutralization of method second The ) (b neutrali (a) Fr Neutrali Pl Fi om IP om ate blo ca xe paci d scre adjustmen Driver tune za A za tion bars ck tor tion adjustmen en ing ts C 1 Tocatho t L 1 PA input compar conductor/exhaust de circuit Ca PA bi chimne vity inner supply as y tmen L R 3 1 To plate t C Neutrali L 5 2 HV Ca C za conducto Sc 2 vity out vity tion adjustmen re adjustment bars C en neutrali 3 Driver loadin adjustmen C er r 4 za t tion t g 125 - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 .. Grid 3.7.4 oftion power amplification, stability,and negative feedback. varia continuous permits capacitance neutralizing of value the conditions, 126 Circuit of grounded-grid amplifier having grid impedance and neutralized for reactive reactive for neutralized 1984.)CA, and San Carlos, impedance Staff, Laboratory grid (After having currents. amplifier grounded-grid of Circuit FIGURE 3.49 capacitances, plate-grid the through circuits output and input the between negligible,not couplingis mayleadsexist the of inductance the because tial If the ofgrids a cathode-driven push–pull amplifierare not atground poten Application Example 3.7.4.1 to used. be is reactance inductive that indicates value positive a and required, reactance capacitive ofnegative value A needed. is out-of-phase neutralization then [4].of sign Conversely,required the is if neutralization phase for equation the solving in If (see apply equations 3.49):Figure following the neutralized, currents reactive the impedance grid and a having amplifier grounded-grid a of case special the In

impedance Z g Z C h Cr ad edn o Pwr rd Tubes Grid Power of Feeding and Care The g − = n C C C n the sign is negative, this indicates that in- that indicates this negative, is sign the f n C j ω − = fg p + + C 1 C gp μ fg ) ( 1

Power VacuumPower Tubes Handbook C Z n μ g

C , Varian Eimac, Eimac, Varian , n Z is positive, is g indicates indicates (3.15) (3.14) - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 Vacuum Tube Principles self-neutralizing frequency the as known is point This concerned. plateis the as insofar potential ment atfila grid placeeffectivelythe will circuit potential-dividing this atwhich frequency, therefore, a be particular frequency. with will There significantly ( current charging the by caused ground and screen and screen, and plate the [4].between voltage division frequency The ating ( capacitance grid-to-screen the ( capacitance plate-to-grid the between action voltage-dividing The Self-Neutralizing 3.7.5 increased. be possible will power output low, quite total the be but will poweramplification the tance, the stage will operate with low excitation power and high powercapacitance tralizing amplification.theplate-to-filamentlessis than capacitance tube,the of rentsmayobtainedanywithbevalue ofneutralizing capacitance. neuthe If independence of cathode and plate circuits thefrom capacitance,the neutralizing while viewpoint the of reactiveof function cur a amplificationis power result. modulationphase will capacitance, grid-to-filament this of reactance the with comparison in small is resistance the If capacitance. grid-to-filament the with parallel in appear will resistance grid a flows, current grid If flows. current grid no which in case the for only useful is scheme neutralization This 3.50. Figure in trated illus is technique This frequency. operating the at reactance zero has that circuit series-tuned a grids the between insert to is coupling this reducing of method [4]. One inductance grid-to-grid and capacitances, cathode-grid Tubes Staff, Laboratory (After inductance. lead of compensation with amplifier cathode-excited of asymmetrical capacitors by cross-connected Neutralization FIGURE 3.50 If the neutralizing capacitance is greater than the plate-to-filament capacithe than greater capacitance is neutralizing the If Anotherimportant property ofprecedingthe neutralization schemethat is , Varian Eimac, San Carlos, CA, Carlos, 1984.) San Eimac, , Varian C fp C fg C gp

, illustrated in in , illustrated Frequency C C gs n ) will not change with variations in oper in variations with change not will ) Figure 3.51Figure C n The Care and Feeding of Power Grid Grid Power of Feeding and Care The . I ) will, however, vary will, ) C fg C gp C fp C pg ) and and ) 127 ------Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 128 can becan made to operate over the total desired frequency range. range If this is capacitorseriesneutralizing the that so circuit the offrequencyneutralizing because the desirableincidental also lead is inductancecircuit in the this variabletube, capacitorthe of frequencyself-neutralizinglowers the the ing self- ableto the operator. If operation is desired over a range of frequencies includ tothescreenuseseries-tuningcapacitor methodcontrol andmakethis avail of the tube and must be tuned over a range of frequencies, it is probably easier circuit. the opposite in to an polarity tube,ratherof the than grid to the probe connected is ously, neutralizing the case this except in that previ described one the to similar approachis This tube. platethe of the to capacitance ( external The tube. the to external added is capacitance plate-to-grid tional example,addi the In changed. is capacitance tube the of up made network variable accomplished is capacitor. aseries with this in exampleshown the In reactance. lowertotal to the ground to involvescase this tion in inductivethe leadadjusting of reactance screen the capacitances ofinternal the device.the between One approach to neutraliza propervoltage givetothe large too division is leadinductance screen the in ing frequency is above the frequency,self-neutralizing the voltage developed operat apply. the circuits When cross-neutralization normal frequency,the operated belowdeviceis self-neutralizing a its When ground. to inductance screen external and itself,device the within elements circuit the by tralized Staff, Laboratory (After self-neutralized. when of a tetrode elements of the representation Graphical FIGURE 3.51 If the RF power amplifieris operating abovethe self-neutralizingfrequency in shown is approach Another At the self-neutralizing frequency, the tetrode or pentode is inherently neu The Care and Feeding of Power Grid Tubes Grid Feeding Power of and Care The Negative Po C sitive ext ) can take the form of a orwire small rod positioned adjacent Components of output voltage 0 V C Figure 3.53 Figure Grid C gp gs , Varian Eimac, San Carlos, CA, Carlos, 1984.) San Eimac, , Varian , in which the potential divider potential the which in , Power VacuumPower Tubes Handbook C ps Ca Sc L s e thod re Pl en at e –E E Figure 3.52 Figure ------, Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 Vacuum Tube Principles Eimac, San Carlos, CA, Carlos, 1984.) San Eimac, grid- external adding by Staff, Laboratory neutralized (After capacitance. when to-plate tetrode a of voltage output the of Components FIGURE 3.53 CA, 1984.)San Carlos, Staff, Laboratory (After capacitance. screen-lead series adding by neutralized when tetrode a voltageof output the of Components FIGURE 3.52 Negative Po Negative Po sitive sitive

Components of output voltage Components of output voltage 0 V 0 V C ext The Care and Feeding of Power Grid Tubes Grid Power of Feeding and Care The Grid C Grid C C C gp gp gs gs The Care and Feeding of Power Grid Tubes Grid Power of Feeding and Care The C C ps ps L L Sc Sc Ca s Ca s re re e thod Pl Pl e thod en en at at e e –E –E E , Varian Eimac, Eimac, Varian , E p p , Varian Varian , 129 Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 130 apply to most systems. adjustments given these however, generalizations, following The make next. a the to circuit to one from at ­varies followed operation procedure for exact adjusted The [4]. be ­frequency must circuits neutralization Most Neutralization 3.7.6 and, therefore, tube suppressof parasitic. the the frequency self-neutralizing approachthe to made be can circuit circuit), the frequency-defining principal the is this (presuming lead plate the of tance screen bypass arrangement reduces the tendency of the and VHFtube theparasitic self-neutralizingoffrequency the increasingThus, tochassis. the occur. higherfrequency theif filament than and screen were bypassed separately to voltageself-neutralizefoundtobearrangementconcerned. areata will This the components zero, as filament is andfar as grid of encebetweentheplate voltagethewhere differ found be can pointinductance, a this ontapped is developed the in screen lead inductance to chassis is excessive. If the filament shownbelow zerothevoltage orpotential,chassis indicating thatvoltagethe is grid The leads. ground screen and filament common the introduced in is inductance Some tube. the of terminal filament the inductanceto minimum with bypassed is lead screen The 3.54. Figure in shown filament and screen generalbypassingarrangementthe theoffashioned from be pentode orcan variable capacitor in the screen lead often has been found to be satisfactory. too great, switching of neutralizing circuits will be required. A small 50–100 CA, Carlos, 1984.) San Eimac, Varian Staff, Laboratory (After return. cathode and screen the to common inductance adding by neutralized tetrode a of voltage output the of Components FIGURE 3.54 If the frequency of the VHF parasitic is reduced by increasing the induc the increasing by reduced is parasitic VHF the of frequency the If tetrode a of frequencyself-neutralizing the changing of method Another Negative Po sitive

Components of output voltage 0 V

Adjustment Grid C C gp gs C ps Ca The Care and Feeding The of TubesPower Grid e thod Power VacuumPower Tubes Handbook Pl at e –E E p Sc re en

pF - - , Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 theamplifier to workthe in normal manner, generating RF powerthe in plate circuitseven though thevoltages arezero. Thepresence ofcurrent this causes If the direct current path is not broken, some current can flowin either ofthese plate theto voltage screenandvoltage supplies, leavingcircuits RFintact.the Vacuum Tube Principles curve curve form or in they shownmay be be tabulated may(or values [3].both). These tube When the valuescharacteristic electron an of values electrical and features distinguishing the identify to used is “characteristics” term The Electron 3.8 regions. UHF and VHF tobut the also time. at same the maximum be neously. should pentode, and of tetrode current the case dc the the screen In mum plate current and control maximum grid current should occur simulta mini resonance, through tuned is circuit plate the When required. usually is circuit neutralization the of adjustment trimming additional small a that found be region,it VHF will the in particularly At frequencies, tions. higher condi operating loaded final the under or oscillations),parasitic for testing be should stage the adjustment, to operating returned condition at reduced neutralization power (similar to that used when the of trimming final For advantages “cold”The of this that system are test voltages applied.high with test a warrant to sufficient is isolation the until made be can modifications Circuit occur. will oscillation gain, expected the qualitative than Actual is less amplifier ofthe loss equipment.insertion made.the be If can measurements prototype with working in useful is nique tech This feedthrough. minimum for adjusted load. be the then and can Neutralization connector output the between inserted is detector RF sitive sen A circuit. grid the into generator signal a from outputpower the feed neutralization adjustments are made until the indicationThe peak. is willminimum. meter RF neutralization,theofout or is circuit the when dip power. When the plate circuit is tuned through resonance, the grid sensitivecurrenta meter RFcoupled will platetheto givetoindication an offeedthrough SufficientRF grid drive must be applied tocircuit. Itprovidewould incorrectthenbe adjustto forsomezero power platethe in grid circuit. current or to cause The first step in the the first Theprocessin step neutralizationof the break to is connectionsdc These neutralizing procedures apply neutralizing notThese only toHF radio the frequencies, to is amplifier RF an neutralizing roughly for tool powerful Another • • present. Circuit adjustments can be made safely because no high voltages are is amplifier unstable. the if stress unusual to subjected are components No

Tube

Characteristics 131 - - - - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 conditions. defined under circuits various in device a of measurements electrical from obtained are Tubefactors. characteristics additional calculate to and mance perfor tube determine to used be may curves the form, curve in given are 132 Family of plate characteristics curves. (After (After curves. NJ, 1975.) Camden, of America, Corporation characteristics plate of Family FIGURE 3.55 operating conditions. specified Specifically,in mayparameters. characteristics These be other shown form curve in for variations and sensitivity, power efficiency, plate transconductance, plate grid while 3.55, Figure tube. same in shown is curves 3.56 Figure of family characteristics plate A usefulness: their to increase forms butdifferent two tion in informa same the present curves These curves. (mutual)fercharacteristics Static characteristics Dynamic Dynamic characteristics • • •

is useful for calculating stage gain. for calculating useful is The constant. maintained voltages are electrode other the conditions that the and platethat unchanged all remains current under oppositedirection, voltage the control-electrode in in change factor Amplification the varying by plate different for voltages. obtained current plate are measuring and voltage curves grid-bias characteristics Transfer voltages. grid-bias plate for different current measuring and Plate curves are byobtained characteristics the varying plate voltage illustrates the transfer characteristics family of curves for the the for curves of family characteristics transfer the illustrates

Plate (mA) may be shown by plate curves characteristics and trans 8 2 4 6 50 0 ( include amplification factor, plateresistance, control- μ ): the ratio of the change in plate voltage to a to voltageplate in change the of ratio the ): Grid volt 100 Pl ate (V C Rciig ue Manual Tube Receiving RCA = s 150 ) 0 –9 V Power VacuumPower Tubes Handbook 200 –18 V 250 μ of a device a of , RC-30, Radio Radio RC-30, , - - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 Vacuum Tube Principles o xrs tasodcac. hs i ti eape .0 mo s qa to equal is 2000 mho 0.002 example this in Thus, transconductance. express to oftion 1 Example product voltage amplification grid of the factor. the and change on effect plate as a current large plate voltage latter toequal the change—the same the has tube of the words,current voltage grid small the a in variation the amplification unchanged, factorcurrent is 1divided by 0.1 or 10.In other 0.1 made be #1)must voltage (grid electrode Example convenience, of a mho,a millionth or( a micromho conductance).of For unit (“mho”the is mho 0.005 or 0.5 by 0.001divided is 1 Example

mA (0.001 mA Plate (mA) • • 2 4 6 8 –30 μ Pl plate transconductance, this term has also been known as as known been also has term this transconductance, plate grid-to- control as described correctly More second. the by divided first the of quotient the is and plate resistance, the and factorcation Transconductance corre the by ohms. in expressed is plate and in divided current change sponding voltage plate in change small a the of is quotient parameter This current. alternating of flow the to plate and resistance Plate tion that all other voltages other unchanged. all that tion remain condi the under it,voltageproducing control-grid in change small plate (amperes) in current change quotient of a small divided by the conductance mho. at : if a of change 0.1 1 made is voltageplate the when if, : : if a grid voltage change of 0.5 of change voltage grid a if : = e V, 1divided plate by is the 0.0001 resistance or 100,0000 –20 270 V Grid A), with all other voltages held constant, the transconductance transconductance the constant, held voltages other all A),with (V . Transconductance may be more strictly defined as the as defined strictly more be may Transconductance . –10 ) 180 V 90 V ( r ( p : h rssac o te ah ewe te cathode the between path the of resistance the ): g m 0 ): a factor one amplifi that in the combines term mA (0.0001mA Family of transfer characteristics curves. (After (After NJ, 1975.) Camden, America, Manual curves. Tube characteristics Receiving transfer of Family FIGURE 3.56 A) is produced by a plate voltage varia V causes a plate current change of change current plate a causes V V more negative to hold plate hold to negative more V V more positive, the control- the positive, more V R-0 Rdo oprto of Corporation Radio RC-30, , μ mho) commonly is used Ω . mutual RCA RCA - - - 133 - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 134 the years, including the following: the years,the including satisfac and insure to study limits performance. tory careful certain within that kept be must characteristics indicate those experience for given are advan Ratings best the tage. to type tube each are of capabilities service Ratings and [3].performance the curves utilize designers equipment help to types characteristic electron-tube on and established characteristics, oper values, typical include ating manufacturers electron-tube by provided data The Interpretation 3.8.1 Various rating systems have been used by the electron-tube industry over industry electron-tube bythe Varioushaveused systems been rating • • • •

ues under normal operating conditions. These ratings, which include of the specifiedtype having characteristics equal tothe published val Design center tubes. industrial and for transmitting used erally operation. of condition any not are ratings too These under used often for tubes, but receiving genare type specified the of tube any Absolutemaximum where tube to the square of the input signal voltage ( sensitivity Power where plate ( current ( voltageplate dc average the of product the to tube efficiency Plate E P I E P b o o in b is the dc plate current in A dc the plate in is current is the ac power the is output W in ac power the is output W in is the average the is dc plate voltage V in is the input signal voltage input the signal is (rms) : limiting values that should not be exceeded with a tube : the ratio of the ac power output ( output power ac the of ratio the : I b ) at full signal level: signal ) at full

Plate Plate : the ratio of the power output ( output power the of ratio the : of Po : limiting values that should not be exceeded with valuesshould exceededwith notthat be limiting :

Tube we efficiency r

Data sensitivit (% y( ) = mh I E b b os P × Power VacuumPower Tubes Handbook o ) = × E E P 100 in in 2 o ), expressed in mhos:

P P

o o ) of an amplifier an of ) ) of an amplifier an of ) E b ) and the dc the and ) (3.17) (3.16) - - - - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 Vacuum Tube Principles ay aig, uh s otg ad urn rtns ae n general in are ratings, current and voltage as ­self-explanatory, but such additional is detail useful: ratings, Many • • • • • • • •

ified elements orgroups of elementsin electronInterelectrodetubes. capacitanceUnless otherwise output. useful the order to determine output in tube the from subtracted must be platelosses Circuit loss. minus inputplate is, that output; tube operating approximate an any is condition for value output power The application. the to ing accord ratings, maximum its within conditions suitable any under with confused be not should values These type. tube each of use the for information guiding as values operation Typical direction the in recurrently it current. to pass opposite designed which is in to that withstand can tube the that voltage voltage plate inverse peak Maximum normal of flow.current direction the in recurrently carry safely can tube a that current plate peak Maximum ammeter. dc a with measured be may(steady averageload),current plate the Under operating conditions involving a rapidly type. duty repeating cycle tube that of dissipation plate permissible the on based is fier valuecontinuouslytube.This be anyhandled for by recti a rectifier Maximum dc output current heater cathode.the the and applications whereexcessive in voltage between introduced maybe used and aseparate applied cathode having is terminal ing to tubes that a safely can itstube stand between heater and cathode.rat This Peak voltage heater-cathode load. todelivered the tube by the power the difference and tube the the ofplate the to suppliedpower is the between value This bombardment. electron of result a as Plate dissipation 1957. were in mum ratings adopted tubes for receiving maxi Design conditions. operating in providevariations notfordo but characteristics tube in variations normal for allowances include ratings These operation. of conditions any under values published tube of the equal typecharacteristics specifiedhaving tolimiting the Design maximum and characteristics operating conditions, tube were both used for most in receiving variationstubes prior normal to 1957. for allowances : the power dissipated the form in of heat by the plate : limiting values shouldthat not be exceeded: a limiting with : discrete capacitances measured between spec : values for typical operation given to serve serve to given operation typical for values : : the highest instantaneous value of : instantaneous the highest voltage : the highest average plate that current can : the highest instantaneous plate current current plate instantaneous highest the : ratings : the highest instantaneous plate instantaneous highest the : , because a tube can be used used be can tube a because , - - - - - 135 Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 136 apr C A., C. Harper, Gray, T. S., applications, electrical for ceramics high-alumina tailor to How R., J. Floyd, Eastman, A. V., design Hybrid Romenesko, M. Mobley,B. J. and Jr.,S. Charles, K. H. S., Dettmer,E. Dettmer, E. S. and H. K. Charles, Jr., AlNi and SiC substrate properties and processing in technology, film Thick Bouchard, J. R. and E. R. Cote, Coors Ceramics—MaterialsforTough Jobs,CoorsDataSheetK.P.G.-2500-2/87 6429. Literature, Product Carborundum coatings, powders, solids, nitride, boron Combat Chaffee, E.L., Ceramic Products, Brush Wellman, Cleveland,OH. Buchanan, R.C., materials, of breed new microengineers CPS R., Block, Birdsall, C.K., Bibliography References 5. 4. 3. 2. 1. • New York, 1991. Industry in Seattle, WA, pp.545–553,1988. substrates, nitride aluminum using processing and characteristics, Levinson (ed.),Marcel Dekker, New York, pp.307–370,1988. form A-14, 011, September1984. 1988. April McGraw-Hill, New York, 1989. San Carlos, CA,1984. Camden, NJ, 1975. Whitaker (ed.),CRCPress, BocaRaton,FL,pp.295–305,1996. ik D ad . hitasn (eds.), Christiansen D. and D. Fink, Staff, Laboratory America, of Corporation Radio in fundamentals, tube Electron D., C. Ferris, Terman, F. E., by the grid as a result of electron bombardment. of aresult electron as grid by the heat of form the in dissipatedpower the of essentially consists and (screen#2 Grid grid)input with no direct voltages present, and with no external shields installed. indicated,capacitancesall measuredare withfilament heateror cold, Applied Electronics , 44–47,February 1969;46–49,March 1969. Theory ofThermonicVacuum Tubes Plasma PhysicsviaComputerSimulation Fundamentals ofVacuum Tubes lcrnc akgn ad necneto Handbook Interconnection and Packaging Electronic Ceramic MaterialsforElectronics Radio Engineering Advances inCeramics h Cr ad edn o Pwr rd Tubes Grid Power of Feeding and Care The , JohnWiley &Sons,New York, 1954. : the power applied to the grid #2 electrode powerelectrode #2 the : appliedgrid the to , 3rd edn.,McGraw-Hill,New York, 1947. , 31,1989. lcrnc Egnes Handbook Engineers’ Electronics C Rciig ue Manual Tube Receiving RCA , McGraw-Hill,New York, 1941. , McGraw-Hill,New York, 1939. , Marcel Dekker, New York, 1986. Power VacuumPower Tubes Handbook , Adam Hilger, New York, 1991. h Eetois Handbook Electronics The Electronic Ceramics Electronic eai Industry Ceramic SM 8 Proceedings 88 ISHM Vra Eimac, Varian , McGraw-Hill, , 3d edn., 3rd , RC-30, , , 51–53, 51–53, , Ceramic , L. M. L. , J C. J. , , Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4 odn E C (ed.), C. E. Jordan, con thermal high having substrates nitride Aluminum Shinozaki, K. and N. Iwase, Technical Philips research, and broadcasting for tubes transmitting power High Vacuum Tube Principles Whitaker, J. C., Strong, C.E.,Theinverted amplifier, in circuits, integrated of packaging Ceramic B., Schwartz, Travis,T.,Gar-El,and R. Horowitz,H. J. A. J. Sawhill, S. tempera Eustice, Low L. A. Roth, A., Reich, H.J., B., M. Powers, Muller, J. J., Cathode excited linear amplifiers, in ceramics, of casting Runk, Tape B. R. and Shanefield, J. D. E., R. Mistler, high of metallization the in manganese of role The Smith, D. H. and M. D. Mattox, Lafferty, J.M., Kohl, W., Kingery, W. D., H. K. Bowen, and D. R. Uhlmann, New York, 1991. Levinson (ed.),Marcel Dekker, New York, pp.1–44, 1988. Symposium onMicroelectronics resistors, co-fired with ceramics co-fireable ture the Netherlands,1990. Electronics Applications Sons, New York, pp.411–148, 1978. Firing Before Processing alumina ceramics, Sons, New York, pp. 637, 1976. Communications ductivity, Publication, Eindhoven,theNetherlands,1988. VacuumTechnology Materials Technology forElectron Tubes Theory andApplicationofElectronic Tubes Radio Frequency Transmission Systems: Design and Operation Vacuum Arcs Solid StateTechnology oeta Brlim xoue hl Poesn Brli Crmc for Ceramics Beryllia Processing While Exposure Beryllium Potential , 7thedn.,Howard W. Sams,Indianapolis,IN,1985. eeec Dt fr nier: ai, lcrnc, optr and Computer Electronics, Radio, Engineers: for Data Reference Journal oftheAmericanCeramicSociety , JohnWiley &Sons,New York, 1980. , Brush Wellman, Cleveland, OH. , 3rd edn., Elsevier Science Publishers B. V.,B. Publishers Science Elsevier edn., Amsterdam,3rd , , G. Y. Onoda, Jr. and L. L. Hench (eds.), John Wiley & Wiley John (eds.), Hench L. L. and Jr. Y.Onoda, G. , , Atlanta, GA,pp.173–180,1986. , 29,135–138,October1986. Electrical Communications Electrical Communications , Reinhold,New York, 1951. Introduction to Ceramics , McGraw-Hill,New York, 1939. rceig f h International the of Proceeding Electronic Ceramics Electronic , 64,1363–1369,1985. , 19(3),32–36,1941. , 23, 297–305, 1946. , , John Wiley & ­McGraw-Hill, Ceramic , L. M. L. , 137 - - Downloaded By: 10.3.98.104 At: 09:03 04 Oct 2021; For: 9781439850657, chapter3, 10.1201/b11758-4