ELECTRONIC URCUlTS 0.WO.IM SEMICONDUCTOR SECTION 3 alphhtical list of oll letter syntnls used herein is GENERAL INFORMATION ON SEMICONDUCTOR CIRCUITS presented below for easy reference. Symbol D.Hmltion 3.1 DEFINITIONS OF LETTER SYMBOLS USED. a Current mnpllficotlon factor (common The letter symbols used in the diagrams ond discus- boa. current gain - Alpha) rims on semiomductor circuits throughout this technicul a FB, a FC, a FE Short-&cult forward current V-afsr manual me those proposed as standard for use in industry by rotlo, atottc volvs the Institute of Rodio Engineers, or ore speciai syrr~hla uib, riic, iio ~,=d!-&~d~h=rt-c!.~t?!+ forwmd not included in the stmdmd. Since some of these symbols currsnc rrrrnsior rviio chmqe from time to time, md new symbols are develop2 to AG AvoUoble qoln cover new devices as the mt changes, m alphabetical Al Current gal- listing of the symbols used herein is wesmted below. It AP Power Goln is rwmmended that this listing be used to obtain the Av Voltoqa goln proper definitions of the symbols employed in this manuol, B ar b Base electrode I"!!?? thcm to assume on erroneous meming. vR common-amlttsr cunent qah - Beta 3.1.1 Con.nuola of symbls. Semiconductm synSc!s ZL' or 'Jbn ~reakdownvoltaqe are made up of c basic letter with subscripts, either lformarly PIE or TIV) alphabetical or numbericol, or bath, in accordmcc with BZ ~m~ss~gnczlbreakdown impedance the fo!!owinq rules: br snnll-algnd breakdown impedance o. A capitol (upper case) letter designates enemoi C or c CO,I.CtOl siocrrcde or curaiiiii circuit wrameters and compcnents, largesignal aevlce CB, CC, CE common boa-, coliecloi, m.2 em:??=:. parameters, and maximum (peak), overage (dcl, or root- rsapactlvely mm-satare values of current, voltage, and power (1, V, Cc Collector Junctlon copocltance P, etc.) Ccc Coupling capacitor b. Instmtaneaus values of current, voltage, md Ce Emitter jvnctlon cqacltoncs power, which vary with time, md small-signal values me CG Cmnt uml" represented by the lower case ( small) letter of the proper Y Collector c-t qum -G-a symbl (i, v, P, i., vob, etc.) CGo O~emllcurrent uoln c. DC values, instantaneous total values, and lmge C IdeP) ~~~l~tlonhyer cwacltonce simal values, me indicated by upper case subscripts C (dlffl Dlffuslo" layer capacltoncs (ie,Ic. VEB, VEB, PC*PC, etc.) Clb, Cicl GI. ;r.piii ccpaciimcl lui ioii.ii.=;. k=i. d. Alternating compment values ore lndicoted by using collector, ond omlttsr, rsspectlveiy
iower case subsciipts; :or vxoxple, i,. !,. 'vet.Vat. 9;. m..-1, inpu, copac1tancs PC. c,~., Cieo, Cic. Input tennlnal copocltance wlth e. Whm it is necessary to disunguish between max- output t.rmlnals shortsVcultsd to imum, average, or rmtmm-squme values, maximum or ac, facommon ba~,ermttor, rmd overage wlues muy be represented by addition of o subscript ~OItectOr m or uv; for example, i,,, Icm,ICM, lcar, ICAV. CL Load sopacltoncs f. Far electrical qumtities, the first subscript Cob, Cocl Co. Cutput t-hal cw~cItLmcefor it-signctes Lke eleclrcde at which the measurement is common hss, collector, (md amlttsr. mode. re.petlve!y q. For device p%--ete:s, +.e first sfibsmipt designates Cobu, Ci;;. C;.= Output temind copacltance, c-c the element of the four-pie matrix; for exwple, 1 or i for input tsmals openclrculted, for input. 0 or o for output, F or f for forward trmsfer, md common has-, collector, md srmttsr, i? i? or r for reverse Umtsfer. nspcctlv.ly -,,. %e secmd sh.scip! ?a~;!!y desiqees !he -, , 5iamnmn reference elecume. E or s Emlttcr slanratl* i. Supply voltages zeindicated byrepening the ED Drolrrtarmlnai suppiy voiiogs, associated device eimode subscript, in which mse. fie --~p!o!m rrmslstor rc!er--ce terninn! isthm designated !a the third Er. Gdatermlnal su~plyvoltous. subscript; tor exompie. VEL. 'icci VLL~,'!:-a. .m,wim trmsLator 1, In devices having more thon ore terminal cf the same EB, Ec, EE Same oa VBB, VCC, VEE type (say two bases), the temnal subscripts me eb, act %me ca va, vs, v. modified by addmg a number following the su'kcript md Ebb Battery suppiy voltmuo placed on the some line; for example Vat-s2. Eior El Input Ctsnnlml network k. in muit~ple-uniidevices L:e :;;;;~Y;ol ~~.bec-rj:ts zo ur EL n.;tp2t &terminal nsrwork me modified by a number preceding the eiecwcde subscript; EF Ernltter foliower, mmputcr loqlc for example,.." Vls-gs CVCult 5.1.: *iph0b.,ico: Lii: ;$ 5;m:;;d.-!~ i-.+2* f er 2~ Forward transfar illhai.. Since the m!es okve me snmewhui cutxtp:ei. u? ELECTRONIC CIRCUITS NAVWIPS Pa),W0.102 SEMICONDUCTOR
Symbol Definition Symbol Dsfinitlon f.b, f,c, fas Alpha cutoff frequency for common emltter current, respectively bose, collector, and emitter, respec- Average ld-cl volie of fotol base, tlvely collector, or emi:ter current, respec- Cutoff frequency tively with s~qnolapplied Power conductance cutoff frequency Total current ot bredsdown volt-qe; Maximum iTequency oi osclllatlon use additional subsmlpts to identify Nolse f~gure electrodes meoswed and condltlona Theoretical cutoil frequency, or zero D-C base current, base reverse- lboeicl frequency biased wlth respect to collector, foac Marlmum frequency of oscillation emlttei to callector open SP~ Power goin cutoff frequency lacs or IBS D-C base current, bose reverse fr Resonant hequency blased wlth respect to collector, f~ nansitioa frequency emitter shorted to collector transfer fI Frequency of unity current D-C base carrent, base reverse ratio bissed wlth respect to emitter, Gb, Power soin for common bose, Gc, Ge collector to emitter open collector, and emitter, D-C base current, bose reverse- Static trrmsconductance biosed with respect to ermtfer, Intrinsic transcanductonce collector shorted to emitter Small-slqnol transconductance D-C collector current, collector Lmqesiqnal transconductonce reverschi-ed with respect fa base, Hybrid pmometer emitter to hose apen Short-circuit forwmd-current transfer D-C collector current, collector base, ratio, static value for common reverseblased wtthrespect to bose. collecto?, and ermtter, respectively emltfer shorted to base Short-circuit forward-cllrrent transfer DC collector cvnent, collector ratio, small-signol value, far common reverse-biased with respect to base, collector, ond emitter respec- emitter, base to emitter open tively D-C collector current, callectar reslsfance, Short-circuit input static reverse-biased with respect to value for common base, collector, emitter, base shorted ta emltter and emitter, respectluely DC drah current, umpolm trmr Short-clrcillt ,"put impedance, small- sletoi signal value D-C emdter current, emrtter reverse- Opensircult output conductonce, blased with respect to bose, collec stotlc volve tor to base open Open-&cult output admittance, D-C emxtter cwrent, emitter reverse- smoll-signol volue biased with res~ectto base, collec- open-circuit reverse-voitaqe transfer tor shorted to base ratio, static value DC emitter cmrent, emitter reverse- Open-drcuit reversevoltage biased with respect to collector, transfer ratio, small-slgnal volue collector to base open Direct current (dc] D-C emitter current, em~tterreverse Alternating current (oc) biased with respect to mllector, BCbase, collector, ond emitter base to collector open curent, rerpectlvely Diode d-c forward current o-c RMS value of siqnol current for lnstontaneous forword diode current base, collector, and emitter. D-C gate current, unipolar transistor respectively Gate tilqser current in a PNPN ib, ic, i. instontoneous value of o-c base, type switch callector, and emitter current, Holding current in a PNPN type iespectlvely switch Moximurn value of total bose, D-C output current collector, ond emitter current. DC Input current respectively Electron current lbm. Io,Iem Marimum a-c component value of Electron cwrent throuqh collector base, collector, ond emitter current, and emltter Junction, reapectlvely respectively Hole cvrent Average ld-cl value of olternotlnq Input current. &terminal network component of bose, collector, and Output cwent, 4-termlnal network ELECTRONIC URCUlTS NAVWIPS SEMICONDUCTOR
Definition Definition Base ,"Dut turnon current 1sw.tcir smo11-.,gnol, open-clrcdit output in9) resistance ib2 Base input fvnaff current lsw~tchingl SI Curient stoblllty factor ii A-C lnput current, lnstontaneous St silicon high-temperature troaslctor iR Instontoneous dmde reverse cvlrrnt SY Vnltaqe stobiiity factc~ 1R Diode d-c reverse current T Absolute temperature, or transformer Is smrurmion cu'=',t .,.." . Amb~enttemuerature -:- (C A >"..Z."...--- .--. J or 1 Electrode, geneid MAG Maxi","", ovallobie go," TC Case tempermiwe MIN, min Mlnimum volue TCBV Temperature coefflclent of breakdowrl NPN Transistor consisting of one P-tse valtoge ond two N-type semlconductoi Junction temperavae ,u"ctlons ohmic delay time (switchmqr jcmlconducfor with donor impurity Pulse fail tlme, 90% in iCie oi ~. z",fi": zs z,Z5==::2:> 311188 :EWIICIIIIIU; Tofol averaqe mower disslpotlon 31 Absolute maximum temperoture oil electrodes of a semior.dactor Storaqe ternperot,xe device Diode forunrd inrovsrv ,>me ~. !-" Average power dissipat;on a: base, -...I/C ".i..__L collector, md emitter, respect~veiy T;:se ;;sc :irre, !14 'r 90% of PG Power gal" pulse (switchlnql PGo over-a11 power qain Diode reverse recovery time Pj or P! Input power Storage time from turr.off pulse to 9CI Po or P2 output power decay t,me Porn Msximum output power Pulse average tune Pt Podcontact open-clrcul? forwad voitilqe tmnsfe: Pbm, Pcm, Pem Peak power diss~pationof base, ratio, stot~c"due ior common base, collector, and emitter, respectively collector, end emitter, respectively Combination of P-type and N-type Small-signal open-circuit forward semlcanduc,or. .lj...... ,- '.___'^... ."tin !=r ce--.-n Transistor consisting of one N-type ease, coilector oad emtier, irsper- an"..:o P-type snmronductor Lively jw.ctions open-c,rcwt reverse voltaqe aonsirr Semiconductor wlt" acceptor Lrnpulilty ;mt:o, stotic volue for common base, Res~sfance,reslsfor collector, ond emitter, respect;ve!y Er?e:r.ai series -=sfs??ar- 'or hnan smali-siqnol open-circuit reverse collector, onn cmltter, respecnueiy voitoge tronsier rotlo for common inrerno1 res,s,ance of base, i~lle~~ hose, collector, and emltter, respec tor, and emitter, respectively tive1y A-C ieslstonce of base, collector, D-C voltage r.?d emitter rpspect,vely, for low- A-C voitnge frequency T-eqdvolen: clrcul! 0-C vo,taqe for uase, coilrctor, Feedback reslstonce und emitter, r; .,>ecf,vely ..-*..'. .- - . .l^sis'.Tnm . A-C voltaqe for br-r, iollector, and L-:i:i-:n.: n^:.."o:i. LnL.21 irzl9lnnrD emxtter, respectlvel) hAdt<>,e?!Y.F.L! :e::s:"?
^"ti": 'Csist*l^r i.o*e-tc-ex,l::er z-- '.-.:L3: 4-!erm,~r,al ne:wo:k o;fp;? rez:sfaace Base-to-emit!.% u-c v0::ege , " , ,,,,-. - Mmcne" ouic.ui resisfui,ir . . . ~ Ezulvalsnf bose h:qh-fr-nuency L"C rev lazco .:.,> :.?: ssv=L :enstanc er,t+er, nase to emltiei open -.".-..7..7..;t .pF,, -,., ".. " .-., .., ---.. -.... ~~ ~ D-C nose floafinq potenflal, emitter reslsrance reup:sr-bmsrd .with respect ?= szal!-r;:q?al, npe--ri.r,.i: reverse coiiccrur, ousc sicr ~rnnafeiresls:i;lic *reaioown uultilue
..mnii-slan"i "YF,I?"L~~, :iii.=-2 c'nar,nr-m-nose o-c uo;ruur
transfer reststance -L..e,- .-.u-L A .: . . .. , .,.. ELECTRONIC ClRCUlTS HAVWIPS (QI.WO.102 SEMICONDUCTOR
Definition Symbol Definitien DCcollector floating potential, VSAT Saturation voltoqe, general emitter reverseblosed with respect VT Thermal noise valtaqe to base, milector to base open W Transistor base reqion thickness Collec
Emitter d-c flwting potentiol. O-C output open, for common base reverse-biased with respect bose, collector, and emitter. to collector, emitter to collector respect>vely open Load impedance VEE E-C emitter avppiy voltage Smolbriqnal output impedonce. VF Diode d-c forward voltage o-c input open, for common hose, "F Diode instontansaus I',-=) forward collector, and emitter, respectively voltage Small-siqnal reverse-transfer VG D-C gate voltoqe, uiwlm translator impedance, o-c input apen, for VG V~lfaqegain common baae, collector, Md VGo over-all voitaqe qoin ermtter, respectively VI D-C input voltoqe, 4-terminal network 3.2 DIODE CIRCUITS. vi A-C input voltage, 4-terminal Semimndunor diodes me employed for rectification network md detection similarly to electron-tube diodes; in addition. "1 A-C input voltoqe they have spedaf properties that mde then pmticulmly Y" Noise voltoqe useful for bias md mltoge stabilirotion. Since junction v. A-C output voltoqe. 4-termlnal diodes mn be mode of the some moteriol as the transistor network md have the same tenperafure weffident md reslstmce, VO A-C output wltoqe they will hack better over the swetempermure rmqe, VO P~nchdffvoltaqe, vnipolm transistor providing nearly ideal thermal mmpmsotion. Likewise, vos Open-mrcult voltage application of the avalm&.e brdhwn phmomao provides VR Diode d-c reverse voltoqe a special voltqestobilizinq (Zmer) diode. YR Diode instmtoneous lo-cl reverse 3.2.1 Junction Diode Theory. When P-type md N-type voltoqe (peak inverse) germmiurn are mmbined in mmufacture, the result is o VRT Reoch-through (punch-through1 P-N junction diode, which has characteristics similar to valtqe that of the elemon-tube diode. If properly biased, the v. Source voltoqe, general Junction diode will mndun heavily in one directicn and very
ORIGINAL ELECTRONIC CIRCUITS NAVWIPS SEMICONDUCTOR liqhtly or practicdly not ot 011 in the other direction. ;he caused by the movement of positive (hole) and negative P rmd N sections of the diode are moloqous to the plate (electron) carriers. Although the movement of holes is the and cathode of the electron-tube diode. The direction of result of the movement of electrans, the charge which moves heavy cutreat flow isin the forward, or easy current, direnion; is positive: therefore, it is common to speak of hole move the flow of light anent (badn current) is in the reverse ment in the valence bond rather than electran movement. h ditecuon. To prohce c forward mrrent flow, it is oecessov contrast, in 0 pure conductor such as copper the cm&ctiOn to bias the function diode properly. Figure 31illustrates band and valence bonds overlop and are not separated by o proper bios mnneciims for forward ond reverse currents. forbidden reg:on: tnus inere 1s m r~iessii: slectr--: The triangle in the grophicol symbol (sometimes colled an available, and conduction is spoker, ot m!y m terms of arrowhead) mints against the direction of electron mrrmt electron movenent. now. It is evident that the polarities and electron current An intrinsic semiconductor is me to which no impurities have ken added, md in which anequal number of electron ond hole carriers exist. An extrinsic semi- P-N Y-F conductor is one to which an impurityhos been added, md in -~hl?h.conduction tokes place primiorily by one typ of carrier. ki
'"0 "P'... ""6 inw it uor,.i~~~ ... ~. *it- ~ii;em;: =?lied ti.1~is i?~"re !id nnd arp charged electri~al!~,the depletim e~6~ni1gito ,:~;clii: cpe~mt?min iater d?scussions. :n region 1s sometime caiird the space charge regio~.! The ---.--- '.,-,.. :r .,,r.. tw,> li7i? l! ;.:::pn: c(I:~:~TcCli ~~ field , o!ertric he!ween the acceptor (positive) and donor . 3,:-. -A ... _ mcaunteieo, iiar,i.y, ?IeC::J:.> 2.. .~.~.... .~.~> ::.e,:!lve: idrs is ;:!!c: 2 bo,,i.t, n-rd the eff~r!ni the . . ..-F-*..-- . -.-. - .hen .- - . mnrn. .- irnpili!e+ tc o serir-iuctor rm~sii50KF rfiirler is consid~rrdto be represented by .y space-charge e!ec::cns :c be rei~0~~4!m~+he!r nlence bm,as wltn eqsi!vlient batteIy (commoniy coiled u potential hill suiiiclent energy to place thtr, ;r.t.e ccr.?ic::cn had. ?he battery). I- the obsmce of m. enternoi fleid, the resultant vacancy cieat& i- the va!ence band possesses a magnitude of the difference in potential across the positive chorge and is caiied 3 hob. ';?"en ilu:cs zit spacrchuige equiyai.nib;ieii !:".is is nnt pr~sentin the VOI.~~*hd, e!ectrons ccn change their ovolloble for external use os a battery) is an the order oi ;er, \,.. Fcergy state on6 conducrior, is Yc,;,',le :i hoIa ~c.:~oc.:!. ,,a .' "- ~.-,.~-... . ., . . . , . ". . ~~ L:rer:Ee, =lt.-i! ,inthe semiconductor 1s connected to the N materlai, ine ]unction 1s sum tii Dt ELECTRONIC CIRCUITS NAVWIPS W0.000.102 SEMICONDUCTOR
N-MATERIAL tt--)P- YATERlAl JUNCTION
NUMBER
ELECTRONS
HOLES ORAWN AW4Y 1 ELECTRONS DRAWN NET + FROM BARRIER AREA AWAY FROM BARRIER CHARGE BY NEGATIVE BATTERY AREA BY POSITIVE 0 I TERMINAL BATTERY TERMINAL - I BARRIER BARRIER AREA I I A N RtGlON ,,,I I I I I Fipore 3-2. Electric Field Relationships reverse-biased. In this condition, the externol battery Iil polarity is the smne asthat of the potential-hill battery as ' POTENTIAL , HILL shown in figure 3-3. Therefore, the bias bottery oids ;he BATTERY potentinlhill battery, and very little or no forward current posses across the junction. This actm occurs because the I holes are attracted to the negative terminal of the external BlAS BATTERY battery md oway from the junction. Similarly, the electrons are attracted to the positive terminal of the bottery and away from the junction. Thus, the depletion area is efi~tively widened, and the potential across the junction is effect- tively increased, making it more difficult for normal current Figure 3-3. to flow. #ith the maioritv carriers effectively blocked. the Reverse Bias Conditions only current that c& flow is that caused by ihe minority
cmiers, and it is in the opposite~ ~ (or reverse current) free of minority carriers, md, since they ore effectively direction. This reverse current is called bock current, and polmized opposite to the majority carriers, the external is substmtiallv independent of reverse-bias values until a reversebias polarity is actually a forwmd bios forthe certain voltage levei is reached. At this voltage the minority carriers. covalent band structure begins to bred down, and o sharp When the external bios battery is connected so that it rise in reverse current occurs because of avolonche is oppositely polarized to the potential-hill battery breakdown. The lheereokdown voltage is popularly called (positive to P region md negative to N region), the barrier the Zener voltage, although there is some doubt as to the voltage is reduced, md a heavy forward current flows: this lonner in ct ::: it KZJ:~. Cnce II~crystnl brc~ssicnn. DIC? :cni~t~nIS :cIid Ifowotd bias. i'?rwwI ccrrent !here is 3 necvy revese iwck. :..r:ert flow wk~:' , 11 13: f13w :s IIw? zecas~the?:cc:rcns of me N req:sn or? re controlled, cm overheat the crystal and cause permanent pelled from the negotive battery terminal und diiven toward damage. If the current is kept at a safe value, the crystal the junction, and the holes in the P region are forced will return to normal operation when L5e reverse bias is toward the junction by the positive terminal. Depending again reduced to the proper value. Tne construction of the upon the battery potential, a number of electrons and holes junction determines the type of bock current flow. A cross the barrier region of the junction and combine. crystal with more N-type material than F-type material Simultaneously, two other actions toke place. Nem the will hove a back current due to electron flow; conversely, o positive terminal of he P material the covalent bands of crystal with predominantly P-type moterial will have a back the atoms me broken, md elecwons are freed, to enter the current due to hole flow. positive terminal. Each free electron which enters the positive terminal produces o new hole, and the new hole is Back current exists solely because the depletion men, attracted towmd the N material (toward the junction). At although depleted of majority carriers, is never entirely the some time an electron entersthe negative terminol of the N material and moves toward the junction, heading for
ORIGINAL 3-6 ELECTRONIC URWlTS NAVWIPS 9m.wo.102 SEMICONDUCTOR the positive terminal of the P material. This action re Even though the depletion regim is less depleted with duces the effective value of the potential hill so that it no forwoid bias, the minarity corriers still exist. ?he flow of longer prohibits the flow of current across the barrier, or reverse leakoge current is practicaily negligible, however, junction, as shorn by the upper portion of figure 3-4. In- kmsethe forwmd bias is in effect o reverse bios tothe ternal current flow occurs in the F region by holes (the minority carrieis and reduces the Sack current practically majority corriers) ond in the N reqion 'by electrons (oiso I0 zero. majority carriers). Externally, the current consists of Tne dynamic transfer chorocteristic curve of the electron tlow ma 1s depenoenr upon iiir bius ;Nii=~y ,",.".."..;,.--*;m- -.--.,.(id- ..---ilillctrnt~d .~ in finurp 3-5. shows how the potential. conducrion vmies wiii~ithe ilpplied vo!:oge. Observe !ha! ns the reveise bias is innsased, a pmn! is reached where the bock current suddenlv starts to Increase. If the reverse bias is increased still further, avolonche breakdown occurs and o heavv reverse Current flows as o result of crvsto1 breokdovm (sometimes coiled the Zener effect). Re mini- 8ARRlER LlM!lS mum bieokdown voltoge :of the junctiar? diode corresponds tc *UP.", I-, *I!,nY"7 EI*D >hip"r;~llm ;;vmsr i;esn VUI:;~~L.[ 1:: C:&i,.>tr~ii,:i " '" "'-4 BATTERY + ------L ---- - diode. REDUCED B4RRIER WITH 1 t, FQDWAWO 8119 1 \ i I I I N REGION
Fiovrc 3-5. Diode Transfer Characteristic Curve
Baslcaiiy, a transisto: consists oi rwo junction diodes placed back-twhack with the center element king common tobtn lunctions Cmnectlng tht. commor! eiemerris ui I*Y iunrtioos taqether externally will na produce proper results, Fiju:. 3-4. ktwter mnnijio~tilr~iias one piece, the PNP junction~. Forward-Bias Conditiess Ir~,"sl~l,,, ,.av, k~ ..",,s;
ORIGINAL ELECTRONIC URCUllJ NAVWIPS WO.M)(1.102 SEMICONDUCTOR
CR1 is farword-biased also, and the polarities oround the circuit are as shown in figure 3-7. Current flow is light (on the order oi 1Wp or less), and junction diode CRl can be considered as a resistor (re abut 25030 ohms). Thus the transistor emitter-base junction bias consists of the voltage drop across diode CR1. Since every Junction diode has a negative temperature coefficient of resistonce, an increase in temperoture causes the transistor emitter-base EMITTER JUNCTION junction resistonce to decrease, and would normally produce FORWARD BiASED an increased coll~torcurrent in the transistor. However, the resistivity of junction diode CR1 olso decreases with an increase of temperoture, the diode voltage drcgis lower, and inneosed diode current flow causes a larger voltage drop across R1 (which opposes the diode-developed bias): therefore. less actuol bias is developed. The net effect is to reduce the total forward bias on the transistor and thus lower the collector current sufficiently to compensate lor the innmse of collector current with temperature. The d-c secondary resistance of TI does not offset COLLECTOR JUNCTION the operation since the tronsistor Lase current How is REVERSE BIASED negligible. However, considering the collector-to-Lase reverse-bias (soturation) current, Icso, which flows irom the base through T1, CR1, Vcc, and Rc to the collector, we find no compensation is provided by this circuit. Tne Figure 3-6. normal current thrr 6 forward-biased diode CRI is so Forward. and RsrnrrBiared Jmrtions heavy that it effea 'v swamps the small Icao current (on the order of 2 or. as compared to 755200 ,ua ior the transistor action. normal cunent). As fa, as signal mriotians are concerned, 3.2.2 Faword-Bias.d Diode Stobilixntion. Tne circuit capacitor C1 effectively bypasses diode CR1 and the output of figure 3-7 employs junction diode CR1 as oforwad- voltage developed across Rc is applied to the next stage, biased diode to compensate for transistor emitter-base through muplinq capacitor C,,, in the conventional manner. resistance variations with temperature. This type of 3.2.3 Reverse-Biased Diode Stobilizotion. The circuit circuitcompensation is effective over a range of from 10 of fiwe 3-8 employs external junctlon diode CR1 as a to 50 degrees Centigrade (usually no canpensotion is reverse-biased diode to compensate for transistor collec- needed below 10 degrees). Higher temperature ranges require tor-base soturotion current variations with temperoture. additional compensation (see paragraphs 3.2.3 md 3.2.4). This type of circuit is effective over a wide range of temperatures when the diode is selected to hwe the some reverse-bins (soturotion) current as the transistor. The reverse-biased diode provides a high input resistance, - itt which is prticulorly advantagwus when the preceding OUT stage is resistance-capacitance coupled.
- -
SIGNAL
Figure 3-7. Forward-Biored Diode Stabiliimion, CE Circuit
Under static conditions, the emitter of transistor 01 is biased positive with respect to the base (forward biased), and current flows through Rl andexternal diode CRl con- Figure 3-8. nected across the source voltage, V,,. In this mndition, RersrscBiased Diode Stobilizmion, CE Circuit
ORIGINAL ELECTRONIC URWITS NAVWIPS 900.0W.102 SEMICONDUCTOR
Two current paths ore provided by the circuit shown in figure 3-9. Tnis voltcqe drop is in the proper direction to figure 3-8. Tne baseemitter current (led flows inter- reduce the forw,xd bias set up by dicde CR1 or.? R1: !!c nally from the base to the emitter, then externally thro~gh net effectis to reduce the totol i.3llrstnr current, to ror- RE ond Vcc, ond through tesistor R1 back to the base, pensate for the inaeqse in tronsi;tor ::si ?ue tc. ternpsi- and is not materially offected by diode CR1 because of its ature increase. lara resistonce in the reverse direction. %e other pth -Ine reverst-biase-; &i0-;? is s~!?..:& !C hci!e " !nrqe: provides for the saturation current from collector to base, soturotior! current (1s) thon the !:cnsistor it at3hfl:zi5, through CR1; VRR: md VCC, and thiough co1lector iond since is consisis 0: the trznsis:;; ;c:-:ctis? cGr:e?! p!vc ., resistor Rc to the collector. Temperature variations in the the current through ii. = icsc + II!. -$nus ii~r diudi emitter-base junction resistance ore compensated for in saturation curient controls t'~.?:ii~;sis!s: I! c!! !!*ln+. the first path by swamping resistor RE (see pmogrophs 3.3.1 effettively reducing the forword bias as the tec;le:o!ire and 3.4.2). Variatims of saturntion current with temperature incieoses md stnhilizino tr,e :o:!ectoi -::;;em: ,Czpnc!vn ore compensated for by the second path, using diode CR1. Cl byposses bth ildes for oc s.i 11:ebiis ciii;li: i: -,:: When a temFrotuIe incrmse muses the transistor junction offected by sigr,a! vorizticr.~. z=v:c!ic- ?xi%! tn rise, the diode saturation curient also 3.2.5 Diode Voitmgc Stobilizotion. 1' ." :;.: :i3r >.->...... -..,.'-:""mA ,~,,rz,,. 3; ,-.$: --"" increases, so that there is no chance tor (he icso currenl uwr La ,=,c.". ".--.., , ,- . ,... .. carriers in the junctiori to pile ap, ixnecse the uzsisror c~nse,h~j! cantjndes ni s low :st? :7 few ~.i.zr-.:-~-r~-,!, forward bias, and couse o cmsequent rise in emitter current. sntll the oj,2.; ;; :car-csri 1s the phi: where /. :??^iies As o result, nitL.ocgh me rct~mtlcncuirpnt moy increase, the breakdown vi~itu~e.if ihe ieue;;r-bin: is in-::.IS-I the emitter NIrenl does not, and there is only a nqliyible kyaad the brrojtcu~x;x:c!, rhr 6lo.i- ,7uFs-; sm,;;:::;, chonye in the total collector current. In effect, diode CR1 current suddeniy mcreases, hecwsr ui tilt ~~zl~i.:hc :!!ic!. operates similarly to a variable gid-leak in an electron md &eapplied voltorre :?noins prncticolly ronstm.t. L. tube circuit. 7he reverse bias permits only a few minmmperes most cases this wiil?est:sj !k dic?r kniuse ni ,-,vpr- of current to flow in the Lose-to-emitter circuit, and main- ?,eitir.g (excep! in the specin; C?S- "f 0'" ;)rw?r -!-file>. tains a hi$ input resistance, while simultaneously com- Redtxtior of the bios helow t5e breakdown voknsje level. . pensating for chmges in Icso with temperature. retuzs the jt-niar to its narmd onpiztio oiz;.: ip:2viceC 3.2.4 Double-Diode Stabillzatlon. The circuit of that no damage has occurred). Lppiicotis;, ni :!,? ::;!::nckt figure 3-9 utilizes two junction diodes in a back-t~inck phenomenon has result~cm the deveiopmw.: cci ;i valtiqe- artanqement. Junction diode CR1 is fomord-biased and stabilizing diode known as the brenkdown dic?e, often compensates for emitter-tose junction resistance chmges called a Zmer diode. - . . ,with temperatures helow 50 degrees Cmtiqrode, as iescrihei ihe Gieafig;,x, >; czz:, ;;,>je;5 7 P!.: :.:=:.:i-,-, in wraaraoh. -. 3.2.2 above. Diode CR2 is reverse-biased moditled in the manufocrxi~nqprecess :i pic.iLce c tc:,.L.- and compensates for bigher teape:atare; cr. di:cuss& be!ow ?c=? \,-l+n:e ;pup: which is closeii ;i,ntiollel. over c Forwad-biased diode CP1 operotes LT tb.e some nonrer ii.ge al fro-; 2.5 to 2?Qvn!!; :;mci~. Loch Zener n~rri~ as discussed in pmagroph 3.2.2, and the ports are ioklim nos a specific bieak:~~~,ic:::;~ :::.i cpe:s!es ?ve: n exactly as in figure 3-7. wail voltage range), iepw,i;z; -:on 1:s drsiT! r.iiil;tii- Reversed-biased diode CR2 can te zo~r,si?.e:cdir.c~e:z- i;:i:;; r.?r-I! he s?!?+-.i in? tip d~str~dauerotml tive ot room temperatures md below. When the ~unctim voitcqe. Because ;: i:s ;;.iTae ;:c:?r!ins, !his 4i"lie h;s mnny uses other thm the basic voitage-i?.;uloting o;pl:;ticr:.. For exompie, it may be used fc: surqe protecrior, us on lrc reducer (ncmzs cnntocf po~r.ts). JS c 6-: zo..-'e-Up, _, ::, :,. nnpiiiier, os a reverse 3lority :rite, or ni : >I.;?;:,,: e!ement. !Is boslc prap~rtiesslil h d~s:usii: :;::. '-l!-.~i-- --:--mnhc in.I~PPI ZP:. " : , 1r.ie-c!nn5i?,7. ,,,,,,,,,---l:--.:r.-r,., ,,,,,. ..,...!\ La l-mtsi ,CC.!." no-,{ ,..Sr$ :1 l,y,": . ~ --..- -1 .L.?.,.. --,, ", . . - .. ,.,--,,,,,= 7:,,p7-7 ;; .;:,,:,;;.-,:.". :,".,~.C." " . . ' . , . . , ., . LIIIYii .,. &,,L ..."- ... .> ,, ?nnrrli,:re rhe r,:;p.?; S:F.&::J,,V:. :c.:;-;c . I. J:?
Fupure j-?. OovblcDiode Stabilixation, CE Circuit
..--eru :".- .-- .,,, ii*.,: ...,.r ,,-- .W,,,.!!V>- -,,,r -"",<,, .....-.,. . . -..- .". - , . - , ^27 ~r..,.~~,-.? .~,,m--,f !:,! tic*: :>,::;z>, s.2, prodzciq o wltoqe drop with the wlority as shown in ELECTRONIC CIRCUITS NAVSHIPS wo.m.102 SEMICONOUCTOR
lain diode VR1 at the correct operating point. Vrhen the itseli). Fortunately, the use of iorward bias produces only input voltage rises, current through the diode increases, a very small voltage drop, depending on the material iorm- and the drop across R1 becomes greater so tho1 the output ing the junction (obout 0.6 to 1.5 volts for silicon), and voltage rernoins the sorne. Cmversely, when the Input units with adequate current ratings ore wailoble to produce voltoge decreases, current through tt:r diode decreases, the desire3 regulation. A particular advantage of the breok- and the drop ocross Rl becomes less so hat the output down diode over the electron tube type of voltage regulator voltoge ogan remzins the some. Should the load resistance is that breakdown voltages are easily manufacturable over denease, and more current be required, the current is a wide rmge oi approximately 2.5 to 203 volts, whereas divided between the lcud and the &ode to ground path, so the lowest tube voltoae available is about 70 volts. that no more current is drawn through R1 and the voltoge Adequate voltage stabilization for quite a w~derange of ozross VRl remains the same. When the lwd resistance circuit operotions rmd temperatures is therefore avmloble. increases so that less current is required, the additional Unique applications of the preceding principles will be cwrent is absorbed m the diode current flow to ground, discussed in connectim with opplicable circuits in other again dividing so thot no oddltional or reduced current sections of this manual. passes through R1, and the .voltage ocross the diode remoins 3.2.6 Shunt-Limiting Diode. The circuit oi figure 3-12 the some. Thus through the avalanche effect, the breok- utilizes o junctian diode connected in shunt between the down diode operates similarly to the electron tube type of base and emitter of the transistor as a protective peak glow discharge voltoge regulator. limiter for transient voltages. 3.2.5.1 Tsmperoture Compsns.tion. Forword-biased Under norm01 circuit conditions diode CR1 is inopera- junction diodes have n negative temperature coefficient of tive, being reversebiased by the potential across resistws resistrmce, and so do reverse-biased junctions until the R1 ond R2. and the transistor is forward-biased bv the droo breakdown voltage is reached. Once the diode is operating anoss R1. When an oppositely polarized input signal (or in the avaloncheeffect region, the temperature coefficient noise transient) exceeds the bias voltaae across R1, diode becomes positive and of a larger value. An uncompensated CR1 becomes farword-biased and condits, effectively diode can vmy as much os 5 percent (of the moxirnum rated shunting the transistor base and emitter terminals. Thus voltage); wih temperature compensotion, however, it is the be-emitter junctim of the tronsistm is prevented irom possible to reduce this figure to ,0005 percent (a few milli- becoming reverse-biased by excessive signal swing. volts) or better. This peak limiting action is particularly opplicoble to Because oforwatd-biased junction changes resistance transformercoupled transistor stages because they with temperature in exactly the opposite direction from the develop transient voltages when the collector current is breokdown diode. ~t is possible to use one or more fcrward- suddenlycut oif by bias reversal. The resulting high biased diodes for temperature compensation. Figure 111 colledor-emitter voltoge with bose-emitter circuit shows a basic compensation circuit, in which CR1 is a reversed-biased cmthen produce strong internal oscilla- forward-biased diode and VR2 is the breakdown diode. ?he CR1 diode is selected to have a temperature chorocter- istic which is the exoct inverse of the breakdown diode's temperature characteristic (if necessary more thm one diode is used in series, but !~suollynot more than three). Tnus the combined resistance of tnth diodes (CR1 md VR2) in series remoins cons:ant over o wide range of temperatures CRI and voltages to produce the desired cornpensotion. The compensating diode must be oble to pass the current taken by the breakdown diode, and should not introduce anv appreciable voltoge drop in the circuit (anoss the diode
Fipurc 3-12. Basic Shunt-Limiting Diode Circuit
lions and cause excessive power dissipation, which could destroy the transistw. In this circuit C1 is o low-resistance bypass capacitor to shunt Rl; it is not used to resonate with the secondary oi TI. 3.2.7 Diode AGC Circuit. Figure 3-13 shows o typi- cal diode AGC circuit which uses the variation of collector current in the second stage to con1101 the diode. Proper bosmitter bias of 02 is achieved through the voltage Figure 3-11, divider consisting of R3, 34, and R5. (Note that at audio Breakdown Diode Tempsrmture Conpcnr~ion frequ~lciesdetector diode CR2 1s in parallel with R3, since
ORIGINAL ELECTRONIC CIRCUITS NAVWIPS WO.WO.102 SEMICONDUCTOR the reactmce of he uansformer secmdory is negligible.) the output of 02 substantiollyconstmt. Since R1 is The potential ot the base of Q2 is negative with respect to shunted by C1 md C2, ond R2 is shunted by C3, C4, md ground md is numerically equal to Vcc minus the drop C5, the (diode is not affected by the os signal variations, onoss R5; it is just slightly negotive with respect to the b.! Ir :sntnl:e2 orl, cv 1-e m:!lt.: :-:.tt:~ XPLCI 111- emitter. This bias, in the absence of ony input signal, ;!!?c?I!- .. !ete:nl?ei 3; Ire .I;: ,clll.~c::OLF v5 establishes the static collector current through P2, which :._.: PNPN Srltchm~iFoul.Loy.r Diod.). :.3 ic .:. is of such moqnitude that the voltaqe across R2 is slightly layer diode is otwo-terminal device which operates in geotz than 'Ca: acoss R!, thereby keepi"~diode CR1 either of two states; an open, or high-reslstmce, sruw ul u atoff. closed, or !ow-resistance, state. It is effectively an on- off switch which cmbe employed as such in switching circuits, or it may be used as a relaxation oscillator or multivibrator. In the nonsonducting state it presents o resistance on the order of megohms, und in the cmd~cting state it presents o !ow resistwce of abut 20 ohms.
INTERNAL DIODE
Fipura 3-14. PNPN Diode Bior Conditions
Fime 3-14 shows tvpical biosina polarity with the
. . junction, +,en, is r~:tlbe-tla;i.? ::.? ?,el? i?. F, :,!?,ns! nonconductlnp cond~tian;this is the resarq cpenz?ii~it. or high-resistance, condition. As the bias voltaye is 1n- creased, it reaches a point which produces o condition similar to ava!anche breokdowr: i.z the :r~itri-o! j>~.nctior., Figure 3-13. and heavy clment flows. Since there is no connection to Basic Did. AGC Circuit the internal junction except throuqh the other sem~conducto~ iilate~izl,the:c is r: %?!! mi~im~m~F.S~S!~?P nl full CUT- As the corrier level of the u~iomingsip-; ir-:escrs, rm,t f1s.v; this is the closeS-::ic,~it, or !ow-resistmce, the increased conduction through ine detector dl~de,C'ii:, condirion. :esults in an mcieasr thiu~;l!~84 sn? D5. %c ~:.>:C~CE..! voltage across R5 reduces he negative potentic1 at the base of 02 (Vcc-En5), tierely reducing tne torwam Dlos zr.j ;.er.ce L",P C"liel:?Ur CLirinl i;s amion oi zs;. .isCne :_ L: :: Ji.;iL;~e;, .LF .;:kz7? across Ri decreases, ma me reverse blos a: ::.Z,;C- [~rwardbas. h?,en,:he 3:ode is fnrwmd-binsei it c~~duc!s,as?, be,=? coanecte? OZI~SSthe o>>tp~~Itwk of 01, it effectively shunts ~rdompsthe slqndl. iCR1 shuts the coliector tank of Gl since the reactonce of the bypass ccpxitors is smoli.1 As a resuit, the rnput oi Gi is diminished. Diode conductim never becomes so hew that it a-,ta - US- - a..+.+ u.c "~cui!-. across the tmk clrcuit. Insteud, cfir,*"c~~nis i;+,;, z.6 :be i:::?::!,,! fe5i=:,7,,-e 2 :;c . . ,... -,-. ,..-< -, -.-- w-."" -,.- i,..,Ini,ii,-,i;,:; :: 1;;'-: Fi. ... 'L ~ , - .. - .. -. .-...... "".% -, .. C.;::~,=I:E! crts 19 '1 rmrinble r~sistonceshunt to momtoin 80.i~Sritching Diode Circuit ORiliiiiii ELECTRONIC CIRCUITS HAVYllPS WJ.000. 102 SEMICONDUCTOR Fi~~le3-i5 shows 32 e1ementa.y wiitchinq diode cir- voltage to point B; between points B and C the curve is cuit in which the hdto!!:ris the ccpacltor to olter- similar to that between and point A. The region of opero- notely charge and dischui;e st a rate determined by the tion between points A mdB is a negative-resistonce region capacitor and resistor t:me c~nstunt.When the over which the diode may be used am am amplifier or oscil- copacitur chorgifig 'v~itngrrelches the diode bretikdown lator, since negative-resistance devices ore copable of voltage, the diode dis:t,ar3ei. the copncitor lvltil the supplying power to the scxe instead of absorbing power discharge voitcge is unable ta substoin the breckdorm from it. con5ition: the diode !hen ceases to conduct, and the charging cycle begins again. 3.2.9 Photodl~des.ne photooiode is a specially con- structed junction diode arrayed so that it is possible to utilize light varia;ions Lvpingmg on ihe junctior, to pro- duce output currmt variations. Both PN and E;? )urnions may be used. aperotion is based upon the fact that phot~nsstrlklng the junctior, pro duce electron-hole pairs in the junction which couse variations in current when the ]unction is reverse-biased. Figure 3-16 shows o typ~calphotodimie circuit. It is essentially a d-c biased junction connected in series with a lwd resistance. Either cuirmt or volrage variations produced in the lwd resistonce may be utilized. Figure 3-17. Tunnel Diode Transfer Charocteristicr The tunnel diode is also of value in switching circuits. Becouse three or more reaions of operotion are rwssible. it is only necessary to select the proper bias and lwd line to achieve different tvws. . of operaticm with the same cir- cuit. Flgure 3-18 shows a basic switching circuit utilizing Figure 3-16. the tunnel diode for three different functions. Under con- Photodiode input Circuit dition A the load line is adjusted so that it intersects the characteristic curve at three points; two are in the positive Normally the pha!odicde junction produces o slight resistance reaion and the third is in the neqativeresistonce reverse current ir the absence of light. When light is region. .Application of a positive pulse turns the diode on, f~cussiliiiri tjlr 2N (or NP) junction, the current through and application of a negative pulse turns it off; thus the he junction is incre-se3. %e aaa!m! of current is m circuit operates cs M offdn multivibrator. Under condition propart!r,:; !u lie i:$;~; 3s rhe iiykr inaezses, the ]unction B the diode is operated in the psitive-resistance region cwreiit increcses, and us the !ilht deceases the ]unction and functions as a oneshot multivibrator, producing a current decreases. Re response of the photodiode is rectanaular*. pulse for each triaaer.* .pulse. Under condition C greatest when the light is directed exoctly at the PN the diode lwd line is set so that it never intersects the jucctim and drops off on either side (*0.5 millimeter) of positive reqions of the characteristic curve, and the circuit the junction rather ro?dly. n.~smell physic01 size, high operates in an astable condition as a free-running multi- effic~ency,low power cmsumption, low noise level, ond vibrator. The tunnel diode con operate at frequencies up to simpie circatry it the photodiode makes its >use particular- 10W megacycles at high switching speeds md appears !y ;ldvantageaus. it is a!ftc!ed adversely by temperature particularly adapted for computer applications. changes and ixumidity. 3.2.10 Tunnel Dlodss. Easicolly the tunnel diode is Because of its newness, tunnel diode applications have o PN junction fondof o si-~irixiuctoimixture which is been treated only lightly in this prograph; they will be irrmgoted with more !h3- henormo! mount of irrpurities. discussed more fully, in other sections of this techincal The resultlnq crystoi has current-'initage transfer properties manual, in conjunctiam with the circuits in which they are which are iif!erent !ram those el the normal diode jlmction. used. Figure 3-17 shows n typicc! junctiar. diode transfer chmnc!eristic p:,,trr,.i us n dashed he,.riith !h~tunrtei ORIGINAL ELECTRONIC CIRCUITS NAVWIPS 900.W0.102 SEMICONDUCTOR CCC 4 INPUT OUTPUT C NONE -P 0. Figure 3-19. 3 PNP Common Base Circuit OFF-ON MY "A 0 --+VF "F C FREE-RUNNING MY Figure 3-18. Tzzse! Oiad. Operatin. Characteristics 3.3 TRIODE COMMON-BASE CIRCUITS. Fioure 3-20. In the commm-mse cncuii, he iripu: s,x.o! :; :-.ec'l? NPN Cannon Base Circuit into the emttter-base c;rcu~t,and the outp~:signal is taken :; ,.: .he collector-base circuit, withthe base element belng The common-base connections for PNP md NPN trm- commm to both. The comman-bose circuit is equivalent to sistors ore shorn in iigwes 3-19 ond 320, respectively, the elemon tu'm grounded grid circuit. I: has a !ow inpu: tigether with polarities md external current paths. Emitter- res:?tonce (30 to 160 ohms) and o high output resistance base bias and mliector-hse bias aeobtained from sepa- (2% to 550K), and is mostly used to match a iow-imped- rote sources so that two vcltage sources are required. With mce -: ...J :i to Gh:-L :-- ?;7m,i, -.,. . L~,-,..,, ed ,.-- !! hos n moxirnum this t~eof cannection, it is poss~bieto ground the base voito- . ,an of 15% n?.a current lain of less than directly for both oc and dc, if desired. The circuit tor o I, with ., power loin oi 26 to 30 dt. 'Rere is nc ?hose >inale .~o!:c~esa.~:ce wi!! he tiiiciussed later. ieversoi ;.tnig. .:r~:x? ^::pd! F~~o~s:bth siqnols ae The semiconductor device symbal 1s used in figures in-phase ma -I the swe polarity. (That is both the input 3-19 md 3-20 rather than the giuphlco: transistor symbo! and output vuiiu ,-s move in rse some dilrcilvo, i.;ci:izr !z: zose -! preyltotim ond understandinq, since it better ..-....*"_ "Y,,, .~,i?i..,,,,,,A,,,, I.'"&i,. ..-.,,= .,...;.-- c :-:e, !h:r>,:;k:':,l2! ::,a ;,~,?;m:;;.~ :ip !l-~ctisnir.?.md mnstroctim of the devlce. complete ?nsit~venno neqative oitemotiuns. 'hhai :he ir.~ 33th the PNP nr! NPN c!rcsi.s mp ihocri twi?:he; s; put siqc! :s ;?s:t?v?, so is the o,irodt siqnai, md v:ce !hei: aperaiion :w be more easiiy compared. Bolh iiirdits verse.; uie farwad-hiosd ',.on em!!ter !o base, ono rrveisrbi~xi !yon col!ectnto base. The po1arit;es oi lhe two circuts h 1s commm, prac::;r I; -ye& of a :'nz;,]~xi ;P,sc? zre oppcs:te b-ro))-~the ~rmslitor~me a: ilpj0siit ;ai;- hetween m inpat mi on i.:pilt signol in both e:e€tron :he psitior,, ond:he cwrents m the external clrclnt tlow in rnd seniconductor discurr.ms when what octuaiiy occurs opposite dirrctiwrs. Note th3: :: !':e %? c!rr-,>l! tile ei- is only o chmge oi poiarl.: :ictaa!ly, Ir. the semi- tmoi current (eiectroni ilorrs fiorn emitre; 10 ccliecta. condunn, when o long urr,r:t iime occurs (with respect to while in the NPN circuit it flows from collector to emitter. the frequencies kmg wpuiirdj, ;iir uuipd sigrLz! is !;;t~c!!;., however, !he flow is aiways irom emitter to delayed in starting becouse of I:.? finite time token for the collxtcr through the base region. (Ctir:ent thecq explains input sqnol ro reach ine output ta:,.~!. Ttis ?e!cy the intern01 flow through the medium of "holes" !or he PNP (1rafi;i: tizc; p:,d9Ly> I!~,,>,-::>:U>;I;~Sk> U,C L",,=,,L----. L,u.,. .,,.. ~.-..- mi"""lhw ioijti. ~o;,i, identical: or even opwsite. tor ro wse; ~risome ,r,srr,u,;rs t;.cnc --.=...- .,.. L: ... z.? ELECTRONIC CIRCUITS NAVWIPS wo.ooo.102 SEMICONDUCTOR in other instances they oppase each other, depending upon circuit cmfiguration, biasing, wd oppiied sign01 voltages. 'The emitter current is always greater thon the collector current, and the algebraic difference between the two is the base current. The bose current will he discussed when it is relevant to circuit action; otherwise, it will he ignored ELECTRON HOLE since it is o very small portion of the total current involved. CURRENT CURRENT In the junction type transistor, abut %percent of the emitter current olways reoches the collector. Tronsistor onion is dependent entirely upon the fact thm the signal applied.. to the low-imdonce inDut. (emitter). circuit causes o current flow chonge which, when transferred to the high- imdmce output (collector) clrcuit,. Produces. a voltaae gain. The current gain (a)of the common-bose circuit is defined os a=L,or the ratio of a smdl chmge @I€ ELECTRON HOLE CURRENT CURRENT in emitter current too smoll change in collector current produced by the emitter current chanqe. It is always less thon one. A brief discussion of the basic current flow in a trM- sistor is included at this point hecause the flow of current. bath internally and externolly, are important to a com~lete understmdingof circuit action. ~iguie3-21 illustrates the current flow in each junction separately ond in the complete tronsistor. In pmt A, current flow is shown lor the emitter- base junction with forwad bias applied and the collector HOLE CURRENT opensircuited. 'The flow externally is by electrons from the emitter to the base. Internally the flow is from emitter to iE LEAKAI base through the majority hole carriers and from base to emitter through the minority carriers. Assuming o value of 1 milliampere for the emitter current, IE, the bose current. is, is approx~matelythe same hecause the collecInr is open (neglecting any external or internal leakage currents). The hole current predominates, there being &the order of 209 hole curriers to 1 electron mrrier bemuse of the Pdopinq effect. Since one milliampere of current amounts to 6.28 x 10" carriers per second, it cm be said that the inteinai emitter current flow consists of 6.24. 10'' holes per second plus 3.14 x 10" electrons per second, and the ex- ternal flow is 6.28. 10'1 electrons per second. In part B of figure 3-21, the emitter is open-circuited rmd the collector-base junction is reverse-biased. Since Figure 3-21. reverse bias reduces current flow to o mimimum, the col- Transistor Cvrnnt Flow lector current, Ic, is actually Ico, the reverse leakage current horn collector to tase, plus my surfoce leakage to the collector, calling for minimum current flow (msid- effects, which me neglected in this discussion. Internally, erioq j:~d:on oios!np only). Horever, kwseof !ne re there is a hole NRent bom base to collector (minority vuse 010s m the coll~tor,:he collector is connectec to cmrler, plus m electron fhw fro- ccll~tort? oase slsc 3 tne neqctive sup~lysc-rce. 'Therefore, the potenual hd! n~nor~tycarrier). Tile ain?r~tyco:iers arerhe case of anoss the coll&c~r junction is reduced, providing m attrac- current flow hause of the reverse bias; the actual cur- tion for the hole current diffusing through the base from the rent flow is very small, being on the order of 20 micro- emitter. Thus, on easy flow of hole current is permitted and amperes (or less1 for a typical transistor. Since the emitter it accounts far most of the emitter current transfer bom is open, there is no flow from emitter to collector, ond the emitter to collector. As a result of base injection, however, base current, IB, is approximately the some os Ice. tne:e is on elmrcm cnen! flow from the mse to emitter In port C of figure 2-21, both the emitter and collector which cmot be collected nrwh the collector oecouse circuits me completed, forwmd bias is applied to the emitter, the collector iunction bier polarity. opwses~. conduction calling for strong current flow, and reverse bias is applied of negative charges. There is also a recombination current which consists of holes that flow into the base: these holes ORIGINAL ELECTRONIC CIRCUITS NAVWIPS (QI.WO. 102 SEMICONDUCTOR combine with electrons befare reaching the collector and On the neqative swing of the input signol, as the neg- thereby cause an electron flow in the base lead and into ative sign01 voltage is added to the positive forward bias, the base. 'his current represents a loss, ond reduces the the result is a redunion of the bias and less emitter current amount of emitter current that can reach the coilenor. The flows. In turn, a reduced collector current flow through Rc current through the collector junction consists of the emitter results in o decreased voltoqe drop ocross Rc and produces current which is permitted to reach the collector, plus the a reduced output voltage; the aegc%,e going oiltput siqnol reverse leakage current, Ico. Assuming chat 95 percent of remains effectively in phase with the some polarity os the input S;qi.d. *e emitter current reaches the collector, the totci current -. can be represented mathematicaliy by a cwfficient a 1 he NPN cirolit shorn iri iiyue 110 !uaaions sim!!m!y (alpha) times IE plus the saturation current Ico: that is, but inversely to the PNP Circuit; that is, on the positive swinq Ic = UIE + ICD (1) of the Input voltage, the mllector current is reduced, and The base current is the difference between the portion the drop across Rc is less negative (or more positive). On of the emitter hole mnmt that does not reach the collector the neqative input cycle forward bias is inaeased, and Cne (the group of holes which recombine w~thelectrons in the collector current produces a greater neqative drop ocross 5~~s)z?t!!e zc!,~rntirn nlmmt. Therefore the cxpress- P,c;thus the output voltage oisc follows the !"put voltage icn for base current is: i;. ;'Lose acd p~iori!~. Is = (IE - ~IE)- ~CO or i B = 1~ (l-i)- Iiii. (2) 3.3.1 Bias (Common Base). Trmsistws are normolly Using the volues of bose current (20pa), emitter current biased by placing a forward voltage on tile emitter-bose (lOE ,ua!;3-d 3!*0 !.95! ISSII~~previous1y, and sub junction (increasing the bias voltage causes increased emltter and coiiector cwirnt iioi), cnl z reverse p2lri:: voltage on the coiiector juncti;;. The ogern!in: !or bias) Using formula (2) for base current md substituting: point is determined by specifying the d-c, nesignal IB = 1030 (1-.95) - 20 = M - 20 = 30 pn (quiescent) values of collector voltage and emitter current. It can be seen from the numerical example that the value of Biasing circuits and orrongements are varied; separate the recombinatim current is 50 pa, that the base current is supplies such as batteries me commonly used, as well as the difference between the recombination current and Ico, so called self-bias arrangements, voltage dividers across that the collector current is the sum of I,, and al~and the collector supply, and other transistors or diodes. that the various internal currents can bemode equd to the ?he common-base circuit 15 usuaily restricted to the external currents. In the example above, the external cur- rent is that indicuted infigure 3-21, and is on electron flow from emitter to collectar with a smaii amount also Lio*ing .. . into the base. The discussion has assumed small-signal 3-22 iiiustrmes a typical single-supply type of orrarqe~ent. condltlons and the use of o PNP trmsi:tor inthe common- Resistors Rl md R2 form a wltoge divider across the bose mnnectian. Nhen other mnfigurations such os mllector supply, with the base connected at their junnion common-emitter and mmmoncollenor circuits me used, and the mitter mnnened to the high side of the supplv. the volues of current change somewhat because 01 the Thus the emitter is always at the highest potential, the base differences in input and output mnnenions and the is at a IOWR mtential because of the valtooe. dmp . across current pmhs between them. When the N?N trans~stor 31 due to thecurmi from the sapply source flowing is emploved,.. operation. is the inverse of 3.4 TRIODE COMMON-EMITTER CIRCUITS. In the mmmon-emitter circuit, the input signal is injected into the base-emitter circuit and theoutput signal is taka from the mllectoremitter circuit, with the emitter element being mrnrnon to both. The mmmon emitter is equivalent to the electron tube grounded-cathode (conventional) amplifier circuit. It has a sompwhat low inout resistance (500 to 1500 ohms) and o moderately hiqh'output resistance (30 K to 50 K or more), and is the most commonlv used transistor circuit wnfiguration. It is widely used for o number of reasons. Because the input signal is applied to the base rather than the mitter, a mnsiderohly higher input impedance is obtained thm in the common-hose circuit. High power qoins ore Figure 3-24. obtainable (25 or 40 db), and an actual current oain is NPN Common-Eniner Circvit possible (from 25 to 60'or better). The actual voltage gain is sliqhtly less thm that of the mmmon-bose circuit high-impedance output circuit. But unlike the mmmon-base because of the higher input impedance, but this is partially circuit, the current gain is not based on the emitter-to- off-set by the current gain; in proctice,voltaqe gain values collector current rotio alpha (a); instead it is based on the of 3W to 10W (or belter) me obtained. Because the signal base-tomllector current ratio beta (P) because the signal is is arplied to the bose, a polarity reversal takes place, injoaed into the bose, not the emitter. Therefore, since a rnak~nqthe autpd siylcl c! opposite plnity to me in?lt small chonge of base current mntrois a large chmge in ~qnd,3s ic tne mnvenu3nd electron t::e 3-.21.(~er. collector cument, it is possible to obtain considerable Tne mmmon-enlitter mnnectlx for ?':? al:! :iP!: current gain (a value of 60 is not unusual). Since the mllenor transistors is shown in figures 3-23 and 3.24, respec- lwd resistance, Rc,is less than the lmd resistance of tively, with polarities ond erternol current paths. Sose the CB circuit, less voltoge goin might be eqected. How- emitter bias is obtained from a seporate supply than thot ever, the increased current in the collector produced by of the mllector-base junction so that two voltaqe sourcesare current gain off-sets the loss of output resistance, so that required. With this typeof supply connection it is possible the voltaqe gain is nemly mmporable to that of the CB to directly ground the emitter both for ac and dc, if desired. circuit. By manipulation of circuit constants and selstion Single wltoge supply circuits will be discussed later. The of transistors, the wltoge gain can be made to exceed PNP and NPN circuits are shown together for ease of mm- that of the CB circuit. CCC Beta is defined as P = with Vc constwit, and is related to al& of CB ckmit bj ,@ rL1- a thus the closer a is to 1, the larger is 4: as a apprmches 1. P approaches infinity. Figure 3-23 shows a smali input signal (v.d applied to thebaseof thePNP transistor. Thecircult is biased tooperate over thelinear portion of its dynamic trmsfer choranwistic. and rests in a quiescent state detemined by the static d-c potentiols oppiied (similar to electron tube class A operation). Assuming o sinewave input, it is opporent that, as v.b Figure 3-23. increases to its maamurn positive value, the forwmd bias PNP Common-Eminet Circuit is reduced, less current flows in the emitter ond collector ORIGINAL ELECTRONIC Cl RCUlTS NAVWIPS SEMICONDUCTOR draits, and the drop across the mllector output resistor (Rc) becomes less, producing o negativeqoing voltage. Conversely, as the input signal swings negative, the forward bias is increased md more mitter and mllector mrrmt flows. The increased voltaae. &OD. across Rc is in a positiveqoing direction, and the output signal renches o positive maximum. It is evidmt that, since the output signal is at apou'tivemoximum wiim theinput slqnd IS at a neqotive maximum and vice versa, the input adoutput palmities ore exactly opposite. Therefore, the mmmon- emitter drcuit is similor to the vacuum-tube mmmon- cathode drmit, pmdudnq o polority reversal of the input signal (dthough not strictly ocmrate, this polarity reversal is mmmonly spokm of os a phose ckffermce). ??..s N?N rilr?lifchow in fi~lreT7.4 iunctions similar- ly but inversely lo tne?Nr nraii. Tnot is, wilm tiie input signal is positive, the forword bias is increcsed. m? Figure 3-26. the collector current increases and produces a negative VoltoprDivida (Fixed) Bias, CE Circuit ,ping outp~coaoss R,. Chi !he neqmive input cycle. the mllectar output is positive; therefore, this cirmit ois, A self-biasing orrmgment 1s shown m iiqure >ii produces m ou~f-phasesiqnal of opposite polarity. It is which involves the internal resistance inherent in tne evidmt, then, that the mmmonmitter drmit always pm- transistor Junctions md is similm to the mntoct bias of the duces a polarity reversal of the input signal. elemtube. The emitter is at the highest positive 3.4.1 810s Circuits (Common-Emitter). Because the potentiol, md the mllector is at the lowest neqative potential, mmmon-emitter armit is more frequently used, it has o so the witter-milector relalion&ips ore mrrem. Since areater varietv of biasina schemes than the other mn- the base is smdwi&ed between these elements old floating, !;3uouons. The mslc prlnc~:les tho~~mremoin rne 53me it is at some intermediate value, determined by the internal mar 's, tne emitter-~asej~ncuw-1st 3e lorn~~Li-bl:~ed resistance pmweters and the internal current flow. The while the mllectar-base iunction is reverse-biased, and potential betwem the emitter and base must be kept to a the d-c no-siqnal values bf bose current and mllenor small value mmpared to that between the collector and bose. -. voltage speci!y the operating point. ~nlsis diwed interndiy by thehiqk-resistonce uciiu~: Figure 3-25 illustrmes o method of using two supply of mllector-bose junction rmd the low-resistance oction sources to produce 3 PriP emittei-hse tias SirGngemcni,: of LL.e e.i!ter-base junc!ion, which provide the desired whih series-aids the mllector supply. It is evidmt tht valtage relationship. The supply voltage polarity is reversed the anitter-base bias voltoqe is the voltage of the mitter- tor NPN tronslstors. By placing resistor RB (shown dotted connected source, while the collector-emitter voltoge in figure S27) from base to emitter, the base is efienively is the total voltage 'between emitter and col:ector, or bth biased off and less base cunent (la) flows. The colle=tor sources in series. For an NPN transistor the polarities me reversed more ewnamical operation is ochieved by reducing the battery drain. Figure 3-25. Series-Aiding Bimr Circuit, PNP The mnnenions for a single voltage supply source biosing wongemen! ore shown in figures 3-26 md FD. -~ne cir~uii VL ;iruil >2: is ;;.;!tag: .'i..-:d=, fix&- bias mrmqanmt, with 81 md RZ mnnected across the Figure 3-27. collecar supply, md the bose mnzected ot ih.e!r mnmon PNP lnlcra~lSelf-Bias CE Circuit ZzncLoz. Tncshe kseis kq! nt n lower ?3 is mnected in series with the emitter. adthe voltage divider made up oi Rs in series with the ~nternolemitter- bose resistonce, determines the proper bias potmtiols. The voitage across RB is subuacted from that of the bias supply to determine the octuol input bios. Collector resistor Rc is chosen to produce the desired operating collector voltage. Tne polarity of the supply voltage is reversed for NPN trmsistors. Figure 3-29. Emitter Sxampinp Circuit In figure 3-30 resistors Rl and Ra operote os a voitage divider across the mllector wltoge supply source to supply Figure 3-28. negative (forward) bias to the base-emitter circuit. This PNP External Self-Bias CE Circuit arrangement allows a single voltage supply to be used for bth bias and collector voltages. When the value of R I 3.4.2 610s Stobilixation. The discussion of the diode toaethei w~thRs in parallel is less than RE, the effectsof stabilization tircuits paragraphs 3.2.2 through 3.2.9, to- voltage-divider voltage stabilization and the thermal mm- gether with the discussion in this paragraph, mvers basic pensotian provided by the swamping effect of RE combine thermol stabilization circuits. Since o number of variations to offer a more stable bias cirmit. Unless the proper of the circuits discussed below are possible, any other ratio is maintained, no compensation is achieved. The special circuits will be discussed in the sections of this stabilization is improved as the quantity manual as they appear. Stabilization as discussed here will be confined to thermal considerations; voltoge stobiliza- Rs. R1 / RE appoahes zero. tion is discussed in paragraph 3.2.5. RB~RI The no-signal, d-c values of mllector voitoqe and emitter current are determined by the applied bias, which sets the operotinq point of the transistor. Under idmi conditions temperature would not offect the bias and the circuit would be thermally stable. Actually, however, a temperature increase causes on increose in the flow ai reversebias collector (saturation) current (Ic~o),and the increase in Icao causes the tempercture of the collector- base junction 10 increase wit6 a mnsequmt increase in saturation currmt. As this oction mntinues, distortion ocmrs, nnd the transistor k rendered inoperative or it destroys itself. To reduce thermal instobilily (runowoy), low values of resistrmce, rather than high values, must be employed in the base cirmit. Refer to paroqraph 3.2.3 for the dismssion of a reversebiosed diode which decreases its resistance with on increase in temperature. Figure 3-30. Another mnsiderotion is that the emitter-base junction VoltaprDivider Bior oad Emitter Swompinp Stabilization of a trmsistor (or a diode) hos a neqative temperature coefficient. That is, as the temperature increases the Copacitor C1 bypasses RE for signal variations: other- miner-base resistance decreases, musing a larqer flow wise, deqmerotion would be produced by the swamping of mllector current in addition to the Uow of saturation resistor. The mpacitor is chosen to hwe a reactance abut current discussed above. To correct this condition RE, onetenth that of the swamping resistor at the lowest a large-value resistor (swompinq resistor), is placed in the frequency to be passed. emitter circuit, where it produces o resistonce stabilizing The circuit of figure 3-31 is o variation of thot of fiqure effect (see fiaure 3-29). ActuoUv.. . in this case the variation 3-30: it uses only voltagedivider stabilization, the mitter of emitter-base resistance with temperature is such a small swamping resistor beinq omitted. In this circuit. R1 ond R2 portion of the over-all mitter series resistance tho1 it exerts fonn o voltage divider onoss the mllector supp:y, ond the little effect on the over-oll ooeratian of the circuit. ORIGINAL ELECTRONIC CIRCUITS HAVWIPS sOO.WO.IC2 SEMICONDUCTOR eff~livebios 1s essentidiv the mltqe existii.2 at $kc the o>llector becomes less negotive because of the Iwer junction oi Rl and Ri. A large resist;:, Ra, is :ui:rec:d pos~tiievo:tage ;roc in resialci i'~.Since the drop across from the divider juncilon wint to :t:e bose ta ?~..~lec ic jpposes the init;ll aios, iess ior;ior4 bios 1s app1:d to higher inout resistance md avoid the shununa effectof R2 tine base tiiough feedbock resistor FF, o~dine collector (R2 is srrnll in wlue bemuse the bsrtc-rml:ler bias is cunrnt outo.~oticl:i sl.;?cses to me oriainu! value (provid- , . only 2 fraction of z voit). The s:ac,;:z:n: c~:~x.n 5.s ed tnzt the grope: ieedjal-k at^ IS rnc~r~tainedj.The!: s:e cirwit is prov~dedby the wltoge &viicr clone, smcr <*.e rwc othe: twes of Er.per.sc:lon icr he arm:: :rc pcr: ,:. 3: divid-r is iens nfiw~edhy vorinrin.is in eitu~.~nr:rll; oi iiiiilr? ?-77: vrli?ii.siiviri~rstohi:izr.lioo iimii~hRE a.nd voltoges thon me self-bias anonoements. The 5isodvontuge emitter cxi?n: ieiirci lhrouqh RE. of this circuit is ticat it acsomes :idre :-i iohsi bec~~se In Liguie 3-33, three iar,alions ai the volla?e :ee&ain 01 the ~ltoqedivider: the circuit oi fqre3-30 is preier- cirolit are shown. 'he cirmit 01 oort A represents voitcae able bemuse of its inneased srnbilfty. feriblck clor!r. &rtiinllvfor 6-c kiosii~,~conditions. Er 7,,.. , - ,.,.- j, c>r;:.:e:e: 3: ::.e 1zs:::x !2z.:i:.: z , i i 4 i 0: + i ;: I .-7': ' !~ . ! ! 0: ; -.: .,, , I -. la, r ,, ; ,# ,h i ?,noti,er zethod of mrnpensatinj fa: ezitter-bzsc :; . j '4j i .-> R7.:i . e . : . : : 7: ~. : :. ~ ~ , \ . . . 2 xc< , , vciroqe wr!lci! 1s proport!oaai !c :,!t :rnyer:tl.!t ;.rui,:% 3er degree. 4i woivnlent retho i ic '3 m! ?*E3CnliV!: ;educe the fommd bios cpplied the c~rcci!. See ii<':re 3-32, in timre 3-22, s~ecircict 2; 3~:;A :ep;esen;s -xL-. :, c and drieedbadn. 'hihen resistor SF is ;.v~ied inic rwc ;mli md bypassed by co"ocitor C os shorn in ?ir! H "1: :pea &-A. I--- 2- -L ..-.- 2 --A -..I,. 2 ? k,"" ..~".:".:-". "U- ,> >r,ui..-, .d.i "..I . - i... ..I ...... "',-". =;er~ Fipwm 234. Thnmistor Bmr,Bia~ Componrnting Circuit A number of thermistor compmvltim circuits have teen developed, but they dl use the same principle of changing bias inversely with tenperature to mmpensate for the chmqe. Flgure 3-35 shows m enitter bias mmpmsator, in which the base bias is omvided bv o voltaae divider mnsistinu of R1 md RZ, md mmpensbting eniiter bias is pmvided by R3 md the thermistor. ?he dm~acmss R3 apolies. . a re- verse bias to the emitter as the tenpemture increases, re- dudng the eminer current mrrespondingly. Figure 3-36. Normally id& thermal mmpmmtion, os well as a TenperoturcStabilizad D-C Amplifier reduction of me number of parts required, cm be achieved by the use of mssmmected Vmsistors arranged so that leokage current (lcso) caused by the internal ilow of minor- the elemmt mltaqes or NrrmtS of one trmsistor mmpensate ity carriers (electrons) from collector to hase. The reverse for thermal variations by pmdudnq mrrection wltnge or ledage current is mbstmtially independent oi mllector Nnmts in the other, while both tmsistors operate as voltaqe and moinly dependmt upon tanperoture, beinq con- omplifiets. For exanple, it is possible to use he variations stant for a specific temperoture, and increasing with temp of the eminerbose junction resistance with temperoture of erature. The effects of tmperoture-mused variations of one Vmsistor to mntml the emitter-base bias of a secund the base-emitter resistonceof 01 are minimized by the relatively large swompinq resistance offered by RE, and willnot have my uppredoble effecton the mllector current, Ic. Thus, whlle the emitter junction is essentially stabilized, the mllector junction is not. Although the collector function is reversebiased for normal forword current, this bias is actually a forward bias fbr Iwerse currmt. Therefore, the reverse Nrrent flow can read values as high as 5 milliamperes. Although this high reverse currmt bes not lead to thermal runaway, it does dmge the parmeters, causing a dmqe in the operating point and resulting in improper drmit operation. In oddition, since the two tmsistors ore direct-mupled, current chm~es in 01 will he mnplified by Q2, causing a much greater shift. While the tot01 base current, IB, is the net result of Icao--. plus thebasrmittn current, the currmt of interest is the very small (increnmtol) chmqes of reverse ledoqe Current, Fipurr 3-35. Thomistor Enittor-Bias Conp.nsating Circuit &so, with temperature; for this explanation then, the absolute values of base current milily be disregarded. transistor, or to stabilize the emittercollector current of Referring aqoin to figure 3-36, it is evident that the main one transistor with the stabilized eminer-mllector mrrmt current path for Icaol is through Rcl, the collector-base of mother trmslstor. Since these clrcult arranqements junction of Ql, and V,. An additional current path which is also the path of Icsaz, is provided through Rcz, the ORIGINAL 3-2 0 ELECTRONIC URNITS NAVWIPS SEMICONDUCTOR collector-hse junction of Q2, RB, the collector-bose junc- tion of Ql, and Vcc Any incremental change of lea01 and of Icp.02 + icBo~will produce on inmemental change in the voltage drops across Rci and RB, respectively. The change in voltage across R,, will be in a direction to deaease the forward Mas of QZ (see polmity indicated in figxe 3-35). whlle the change in voitoqe across Ra will be ir. a direction whirh incrmses the Loreaid bias of 02. Ii the values of iic I and RB are chosen so that the incremental c!.~nge of voltoqe ocross Rcr is ~light!~greater thor the ~ncremental change across RB, then a thermally coused increase of ?.llector ccrregt w:ll be sompensatpd !or by o :eductlon of he fo:wr? hias r: :r:ZS:5!2r $2. The dismssian otove mnsiders only !he very small -i----:- -,--+ nrl+~md hu far?ern!llie variation in the -..- .--- ... ~ .~. mllector junction ot Ul: it rbes not mnslaer tne static Figure 1-37. PNP Cornmom-Coll.cto~ Circuit >,", qeT;p-, -.--it+-. ,,..-. -.ili.,.mn,nnu...~..... rp,ictnr Fi,, nnd hwsd by supply VES. The Input sicpol is appiied across RE and amplified by Ql,appearing across RCI as o direct- mupled input to the base of 02, a mnventional CE amplifia, The output of the tw stoges is developed across mllector Imd resistor Rez. The coilector supply for both stages 1s taken trom the ssiqle Vcc source. For a complete dis- cussion of ds mnpliilers, see BC Amplifier Cirmits in Section 6 of this tedlnicol manual. 3.5 TRIODE COMMON-COLLECTOR CIRCUITS. Ln the comm~ollectorcircuit, the input simd is injected into the base, ond :he output signd ts tdm from the emitta, with the milector being common to both cirmits. - Ite mm,~~i-min~:drcdii is equlrdeir; :? t:,e €!ert:o: tUDe cathode-iollowa orcult. it has a hi+ input resis Figure 3-38. tone (2K to 5WX) ond o low output resistance (50 to is00 NPN CornrnorColl~ctwClrcmit ohms). I! .".as o mrrent gain similar to that of the mmmon- emitter aimit, DL~:a law6 ~wergas !!ha:eiiha the ,ZS as; The aqmt flow md urmslstor action of the CC drmit CE circuits (10 to 20db). The output signal is in phase me as explained for the mmmon-base connection, but the and of the some polarity us the input s~qnal.md the volt- wrmt goin is no1 based on the enltter-to-oollmr arrrslt ugr @,is &; , Thj. .ir?.!! 1s ,254 ?.!!a, dpho !a): Instead, it is based an the emitter-to-base n:ostly !or impeCance-matcki-.g md iiolotion of output current ratio, pma(9, ternuse the output Is tkm from stages; thus its funcdon is similiji i~ ?ht of ',,e e!ect.m .L.,,e emit:e: d:&t Slnce a small change in base current cothdi fallou~e;. :: '.-2 L$e ~Yiity!o ~sssignnis in controls o lorge change in emltter (and collects) current, either dlrectim (bilateral operation!, a feature whlch is it is still possible to obtain cmsiderable cment gain. part~cuiari~useiui m swir:bj iii~uih~. iixsie;, since 'Ce ??rl??er cur-! :a!!! !s offset tr! the low -. " - -- . > i,;ljiis >,< *>"L-JY i-,;-< :.:c .=:l ! creases to its maximum positive value the forword bias is re- heed Thus, the mitter md milemr mrrmts ore reduced. produang o decreased voltage drop across the emitter output resistor, RE, ond producing o pasitlve-pinq output voltage. Converselv, as the input sional swinas naative the forward bias is inaeased mdmore 8nitte-milector current flows. The increased voltoqe drop ocross RE is in the negotive- going direction, and the output siqnal reaches o negative madmum. Since the output sianal varies in the smne dir- ection os the input voltaje, both reaching their positive ond negative maximums simultanmusly, 11 is widmt thot these signals me in phose. Therefore, the output of the mnman- mllector arcuit is of the swe phase and polarity as the input signal and no phase reversal is produced, just as m Figure 3-40. mmmon-base operation. klf-Bias Circuit The functioning of the NPId circuit shown in figure 3-38 is similar to, but the inverse of, the functioninq of the 3.6 TETRODE, POWER, AN0 SPECIAL PURPOSE PNP armit. Ilhm the input signal is positive, the forward CIRCUITS bios is inaeased (its polarity is opposite ta *.at of the PNP In this pmagroph, various types oi tetmdes, powa mn- circuit bias), wd the emitter mirent inamses ond produces siderations md power transistors, and special purpose o positive-going output across RE. On the negotive input transistors and their basic drmitry are presmted Vihile cycle, the emitter output is negative; therefore, the output it is possible that mmy of the special purpose items will not be of this circuit is also of the some phose and polarity as the mmuntered in Nwal equipnmt, informotion on these items input signal. Thus. the commoncollector circuit always has been indudedbecouse of the rapid odvmces in the produces on in-phase output signol, regardless of the type stme of the art. It is anticipated that, in later revisions of transistor used. to this publication, the information concemicg those items 3.5.1 010. (bmmon-bll.cte,). Comrnan-milector bias- hidhove the greatest application will be expanded ond the ing schemes are similm to those of the CB ond CE mn- informdon mncerning those which have little use will be figuroticns, md the basic principles are the snne. That is, deleted or will indicote their limited application. the base-emitter junction is forward-biased the bose 3.6.1 ~nmd... The addition of a fourth element to o mllector junction is reversebiosed, md the ds, no signal transistor produces a tetrode transistor. Both junction ond values of base current md aollector voltage specify the oper- point-contoCt transistors cm be formed into tetrodes. In ating pint. the junction transistor the fourth electrode is essentially Figure 3-39 shows a setiesaiding bios arrangement in another base electrode (921, whereas in the mint-mntact hi& tm, voltaqe supplies are used. This orrrmqemmt is type it is essentially mother enitter (E2). simi;ar to that for the CE circuit shorn in fiqure 2-25, and 3.6.1.1 Jvnoion Tenod. IDovbla-60s.d Tron.lstor). the operation is du, similm. In figure 540 a single voltoqe The junction tetrode consists of a mnvmtionol junction source bias mrmgwent is shorn. Note thot the flow of trmsistor with mother hase electrode (B21 added on the current through RE is in a direction which produces a volt- side opposite the Bl mnnection. The Addition of proper bios age drop that opposes the applied bias and collector voltaqe. between the base dectrodes decreases the mllector cap- The actud bias is the algebraic sum of the two voltaqes. acitmce and the bose resistance, md thus improves the Polarities md mrrmt flow areopposite for NPN circuits. high-frequency response. As compared to a conventional junction transistor which has o hiqh-frequency cutoff of opproximotely 30 mc, o tewode will hove good response up to 100 mc. Fiqure 3-39. S.ri.r-Aiding Bias Circuit Fiqur. 3-41. Junction Tetrod. Cirtuil ORIGINAL ELECTRONIC CIRCUITS NAVWIPS POO,WO. 102 SEMICONDUCTOR Figure 341 shows the boslc tetrode arciit. The Y.131: transistor is used osm ill~straisn!or eose a! egluininq MODULATOR the opeotion. The teuode 1s mnnecfed in the same mmner INPUT*- os o triode, with forward emitter-jlnmion bias wd reverse I collector-junction bias. &tween base l ans base 5, however, o large voiue of voi:o;r 15 mnncnzd (on the 0:dt.r of mlts 0s miipored w:tn rmrhs ai o volt), id: oh;: VMM VEE i i i; volts. Since the hemutrriul is semiccnl;c*.a: %,b th..e 0 0 paints of ~ppli~llflo-.ore on oppasite sides, thse is o de- WTPUT finite resistivity betv+es,3i c;,i32 *::cr irshces a uniform drop aaoss the base (if the base were ohmic, a short drcuit would ensue). Since the apolled hose $135 1s aqotive mdiwge, it :loik; elecna c;::tr.t floli !?mdsh ail >arts of the 3aje reqion: excep: for o smd! volme L- 3 '-L mnventiond vccam-tuae .?lxtr, b?' it "perales hetter at emltlers ore used toqether, the currmt loin of emitter ?lo. high frqmdes. It is superior to i:c mnvmtior.nl crystal 1 is enhanced considerobiy, fram 4 to 8, which is roughly diode or tnoce mixer. 2-1/2 times t,ie original value. Eritter No. 2 may be used Tnemixer tetmdeis mnstructed with twoemitters md 1s on lnput control elemer.!, if desiied, ant the cmrent .join one milector 0s shorn in !ilure 3-44. ?'he Brltters ore ,:ill vov according to the in?ut siqnzl. 'heinneasein current iain whm bth emitters ore properly biased and operoted simultaneously results from the foct that the mncmtrotion of holes inject& by the first mitter atttocts electrons awoy from he base regon, betwem the semnd enitter md the collector. This reduces Lbe possibility of electron-hole remmbinations md ~lobles may of the sand-emitter injected noles lo rmcii the ml- lector, thereby incrwsinq t+e flow of mllector mrrent. 3.6.2 POW.. Trmsiswrs ond Considaroti~ns. Power trmsistors use sp&d mnstruction rmd desi~mnsidera- tions to achieve rated output. The conventionaL~transistoi is usually operated of low wltoges md low values of mr- rmt, whereas the power trmsistor 1s operated at relatively hi94 wltoges adhigh mrrmts to prodce power outputs. The classification of power transistors, however, is some- what arbitrary, md does not indude he meorder o! volues as used for electron tubes. For exomole,. . transistors of from Figure 3-44. 2 to 50 milliwotts ore classed os "on-power types, from 50 Cryrtol Mixer Tetrodr milliwotts to 500 milliwotts Il/2 watt) os low-oower Noes... . fram 5W to 1000 milliwotts (1-wott) as mediwn:power types, locoted ot qddistmces on opposite sides of the mllector md all over 1 watt as high-power types. ur hot toth emitters hwe the sane effect on the mllector. Becwse the trmsistor is o nonlinem device, it hes not ?he mllmor outpct is equd to the sum of keoutputs it respond to large siqnols (where variations in mllector voltoqe wuld have if each mitter wereoperated sep3rately, pm- md mirent me a sigiificmt fraction of the total rongeof vided that the collector is not given into saturation. of operation) in the some mmner as it responds to small siq- 3.6.1.4 Point-Contact Totrods. The conventional point- nols; hence, smoll-sipd parmeters me used to define non- mnloct four-element (tetmce) trmsistor differs fmm the power (linear) operation, md Iorqe-siqnd parmeters are spedally mnstructed crystal-mixer tetrode discussed abve used to define power (nonlinear) operation, Small slqals in bth opnation and cor;st.ction. Emitter No. 2 in the cm arbitronly be defined os those whid me less thm 1 wlt, point-mntoct tetrode~sspaced c! greater distance from the ondlarge dmds as those whicfi me Greater thrm I wlt. mllectot thm emitter No. 1. Both enitters are fatward- Since it is possible to have o mall siqal drivinq a power biosed md the mll~toris reverse-biased, as in a junction amplifier, it can be seen diot sometimes either parameter trmsistor. 'hhm mitter NO. i is mnnected md emitter can be used to predict circuit perlormance with good No. 2 is left opm, he trmslstor operates like o mnvoltional ~pmdmotions. triode wit) o mrrmt loin of 1.5 to 3. '({>.a mltter No. 2 'While toth point-mntoct ond junction trmsistors con be done is used because of the qrwter spaall !mm be ml- used as power ampiiliers, the point-contact type is usually lector, the mrrmt gain is small (abut 0.2). \%a hth limited to values not greater thm 1 watt. This limitouon is due to the foct that the point mntact is unable to cary o heavy cwrent without excessive heat in^ and consequent donage to the transistor. 'he power trmsistor must be oble to oissipote the internally generated heat while opercting at the increased tmpetoture resultinq fro= its omheat. It must olso be oble to operate of high arrmts ond voltages without breoking dorm or cousinq excessive non-linearity (distortion). S~ncethe junction tionsistar does not concentrate the heat around o paint saurce, but spreads it thmu&out he junction, it has a definite sdvantoge tor pawet use. Both NPN md PNP junctions may be used, md they operate fundomm- tally the sme regmdless of the wehod of mmu!acture (grown junction, diffused-junction, dloy junction, etc). The curent rating of o power trmsistor is the maximum mileclsr mnmt that con safely be cmried by the trm- sistor, without exceeding the power rcting, cousing internal Figure 3-45. donoge, or piducinq an excess1.e !ass of current ,pin st Boric Point-Contmct Tetrodc Circuit higilcr emitter curents. ORIGINAL EL EClRONlC CIRCUITS NAVWIPS W0.m.102 SEMICONDUCTOR on one holf of the input cycle and that the other transistor ?he voltage rating of o power transistor is the voltage works on the othn half of the cycle. Reput-oi-phase for which a specific ledage mrrmt ocmrs for a specific outputs me added ot the proper time (in-phase) to produce circuit mnfiquration md operating current. m output hom the load resistor which is equd to the com- The paws iotinq of the transistor is the moximum bined effect of the collector currents. permissible poivei nkich moy be sa!ely dissipated by the unit wiihout exceeding the maximum junction temperature --A --..-'-- Am--. nr nu-, "*rind "f rime. 1." l".,...l -l..lyb z ...Ine sotwotion voiiage is ihe ~duebelon n:licb the collector voltage cannot be !;rfi.er reduced, even by iincreosing the input current. 'he thermal resistmce oi a transistor is the ratio oi the difference in onud power rating with respect to the rise of tmperoture of the uansistor. It is commonly expressed in degrees centiqade/rnilliwatt, or wmt. Ibei-d r;.: ;;.:trf2r2i..cc ::a;10-5 -- ,,.= 5 -.., ?.- ,<.2: ::r,:.:z.:.:: ;x.*:.;--,;!c.: '!:!cz$ :t. m~mteredmtk viorotors, qenerorar~,or dynmolors. 2.5.3 spssl~L=~uiposerron.i.lw~ and Circuir.. ?he special-purpose transistors m,d circuits d~sc~sed!n ORIGINAL of its hi@ey nlise :t;d, imklc.e ?lirer:5, m-. iin.ite6 circular P-allay (called thegate) which encircles the bar is fre:+enx resmsr. reverse-btosed tothe sourcegid of the tor. ?he field effen produced by the reverse bias depletes the area benmth the P-electrode of current carriers. Reinput sip nai mries the basic cnnductivity of the N-ba wd effect- ively controis the wrent supplied by Murce. ?bus. current flow thrw* the lmd resistor produces a cures- pondinq but amplified output voltage. Since the predominmt canler in N-type material is elecmns andthey ore mnuoUed by the electtic field betwe~lthe gate and swrcegid of the bar, wd since holes are not involved, the term unipolar was derived to indicate that mly me mrier is involved. Ihe adwntoge of this type of device is that o small signal controls a much greater output, vhich is limited Figvre ?-47 shows t~icdMm mnndons an&the essentially only by the size of the source supply and the mrmqmen: oi LYE i:~,~~cS: :hi- !:%s!str?l. Pie t:msistor resistivity ofthe basic bar material. Applications are some- essentially rnnsirs of I mnv~ti3rd'liod? two-iunc:iw what limited by a rather high noise figure. PNP i1r.i: mtn a, deer :;-':r:zir~ si ,~:ISCLU 4.3e emitre: P--nee (j!) s;c : . .x;!-,F ,r t:.i c: 1::) 2s fcrward- biased. the base &men is q?;niei. o.:rte second P- INPUT xea is le? !!m;nj r.?tnzs. :I< ?.. I-! b.5 a result, the nidde NP ]~.~i:isn(-2) ??;x.!vc~.; W:SW biased Hmce, heP1, Ni; ;rd Pi s.\-t~srsae ampaable in anion to ol ordimq .:i::ie .rmsjs-r;. 7-r liootiny P2 region, howev~,zcm~;ss -1 iei :ar!!3-i:. i :T.- i. 3.) potentid OUTPUT hill due to the dqk2tion rq;on 9 jlcz .- : .. r 2-5 c qrea: rR.lrdingeffeuronthe;;1?s!r~,~ .1.?r:r.:.- CLI,~.:; 3 "space &age" G! hies -3 x:!LC tin .i'?Z 516-1 ~f J3. neresul: o: tn;s is a :e;;.rim ?i he;: i:r,mion rei.!s!mce, there* dlcwing inmelst? eiect~nnover2n: iron t?e tvi section into the Pi c%;;c:.. 3erc-ip.ete porn tr,i this current (excep: the sld pcri m:;h rmmbines wrn me of the holes) is :rcn tho ;:el;t:i- :erain'! o! Vcc to N2, P2, Ki, bsse I=;. .i.iiack ;L icc. Fipvrs 3-18, Lmge values ci 21rrmt amplificmion may be ootained Unipolar (Field-Effect) Transistor sinc? 3 relot.,eii: s.r,u.:! xc~n,i!7!;ai.C! hdes in the P2 saem qi?s:ise lc o *r~..'.!:ge; n;~;cer si elst:i'rs trom 3.6.3.3 Urnliunction Tronslstor (Double-80s.d Diode.) the Ni rqon. Control ni tne -r.l!?e,gr a~m:is cb:ci-d The siiico;, uniJiiilction transistor is a thret-terminal since i: is detem,in+ by 15e :;.:i,>n-i r;! ;'trcrppedf' hies in semiconductor device, sametimes called a double-based the?? ?@on, wlch :ti turc is 37.?~i?i. ?y he anitter diode, which is unique in tiot it can be triggered on by, or Lurrmr; ?he m.itt9 cur:m', o, :GUISE, is jeierr~inedjy the an output canbetaken irom, each ofthe three terminois. input siqnnl r? tce 'rmsi;tar. T;? -me ic~kcoilrct~~ is Once the unit la triggered, the emitter axrent increases der!ved bom ti.e :rmsrs:c: wnq &:<:an, nhij, resembles a hmk. NTNP !r-lis,s:.;i- icic ds,, k.rcm~focturrd. ;he b.mk tra\s:itor :>;'ia:hs ,34 ~i m~!iij8nd shwid not be mnfused wit: br P:+?\,' :,,~v;ci, nr the siiimn- controiied reaifief which s?Pro?es ii-nila:iy to a thyratron tube. In the PNPY ti!&& sw,tc- :I mt~lledrectifier, the mndP-mm is illn~~sri; co!d ?,,ion, whereas in the hrok mllstoi it is ieir flo.~t'ng. 3.2.3.2 ~n!prior(F!.Id-EHe:t Tral;:~+~i). mi- poior transistor use5 3 'ii.ime ~o~s'li,ctkrto utilize the effect of an e!ectric fieid :a cr.)tio! tne aassoce 3i current carriers !hr:.ugh the bcsic semimnductor iw. It offers o hi&. input. r2s:stms-e (abut one rnelohd. . w~tho rr- iativeiy hi6ouput resistmce and cod r.lgh-fre~~eicy respmse. Figure 2-4i shor.s i.r ii;s,; 1;.:!~,1117 [.;TC~J~;_ %e basic N-qemnr>um iilr hos a .x!au-i in3il& 'wtween :he .source Figure 3-49. mC mi +-,TI, - : .:;.as ,.: . ? Uniiuncti~mTransistor ELECTRONIC URWITS NAVWIPS regenemtively until it is limited by the power supply, thus. Resistors FU and H4 h figure $5i inrx n Slos vcltoge the donof the msistor 1s similm to that of the gas divik forthe eo;ner, vhid nc%cl:.; bids L4e circuit or thymuon tube. It can be employed in o variety of circuits, ajtoff, kr input appUM '1~~3~s34 W(U pihce 0 r~iatiiely but it finds Its geatest usefulness in the switching and high-voltage outpit ac?ss R! md 1 rehi;uely low-voltage pulse fieids. cutput ;=TOSS 92. !':. !r:>:i r_.in_;? .id will produce wgut Figwe 3-49 shows the hsic uni:unctlm bias m- oaoss Rl ;?d PA. LL~~w!sE,m h"ut op?lid acmss R: nections. The unijunctiun transistor cmsists of an N-type will pid~ceo\irputr ocrccs :? ad ?4. c;--. *he =lil, 7 kc, :, reirz~emlidir- silim bn with two ohmic hse mmns ui hr e~ds~72 .:; mr smsluve, cm2 ,:.> k ;2- 5,1~pe:z:.C-~.1~i~.irlvpan- P-tvoe'. emitta fPN. .junction) near base No. 2 lH2).. . A mse his biasing potential, applied between the two mse mtacls, t~:qpLl%..r '!. utdizl.2 :be .,orlotion ot reslst'viry o! establishes a wltaae oradient alms !he bar: the emtttw is he base wit? te; *..?lure, ihe mrermse rrsistrimr ji- located nearer B2, so ;hat more th& half of .the he% bias creases wi*. te.y :: :n? a! a pmC?IcolI~cmstont rate. A along the bn appems tetween the emitter and base No. i. 1 dueis : ' *.ice?,: pi 5-s c. If an external potential is applied bet- heNo. 1 and 3.6.3.4 &r!-r.-forir ?r~sir*r- Tne silii,jce ,he -itter mmter thm me internal voltage gmdmt iu:ier t:.~,.;;-!c: I r . 5!2~:&!~i-z:sil!c?..ir ie;zn>~r: . 1 .>=. betwe% me same pomts, the jur2sSur. ;:;;;;,-i-~icse& ii -., .~.T ; . z : ..: " .-. .-". he externd pctenti-! is less Cim lh- !nt?mni voltaqe a tor ii: SPI~IIGT:..It h35 :!w-i ?!311e (.mi(.- rn e*.c~?lmt reverse-biar is poducm. Normally, reverse bias !s ap bL::lllr;~~m~respcnse ',rrc!-!-it t2ce i? figxe 3-50. ".<;*&-:.~,-,;+,; ~ ~;;;;;,;;r:p: :;.+$:s. F!?-!ie.c: ,?i~~~?&.s . . . ..- .'..... ;.. .- . :.., ..<,. ;*, aaaeja-ga ~7.~z:< c-i.x,Lc; ="s.-.-<< ,..< ~:>. -- - ..-.. i"iieliosi,. (j~?J~op.LICTCS GO3 V.C. s:,~:o&CZ-~IT.; ei!m: tn.f 1s. me eimliac iisiar *!.A::; c.,r.i;z z Zs --;'~::- -I ie, ger~rn,~ rrciudes toth holes mo e:-ne %.:L u .. . ym.n +*, ga- Sys ~~:~~,T?.S2??.tT- .=<-:.m F.w<,! ?!F. trode LO :hi twmm&jl~;r!ucsi. ; m~~c'i31?i P! ioies . -- (Y"'-.--'... ,-.., ,- type transistor. Their basic difference is in consiruction; 3.6.3.7 Diffused-80s. (MESA1 Tcansirter. The diffusd an inohsic area is inserted between the base and collec- base transistor utilizes manufacturing pocesses to produce tor areas. lleover-all result is to reduce the base-to- o physically thin diffused-base alloy on a basic germanium collector capacitance and prmit higher-frequency operation hi. Thusthe collector-base cwacitance is reduced, md (on he order of 920 mc maimurn). the slowness of the diffusion process through the base region 3.6.3.6 Drik T.mnslstor. This transistor uses a is minimized. Better high-frequency response results. consbuctim which qaduolly chmges the resistivity of the 3.6.3.8 Sllim Controlled Restif~u.The silicon semiamduct01from a highly conducting material at the controlied rectifier is a silicon 3junction, ?-terminal emit- to 0 more resistive material [nmly pure germanium) device. It is the semiconductor equivalent of the at the mllmor. When a pstentiolis opplied betwem the thyralron I&. It can be either o PNPN or a NPNP unit. emitter and mllector, an electric field effect is produced in the PNPN unit, the mode is the P terminal and the which muses the internal carriers to drift across the cathode is the N terminal. The internal N region is not junctions at high velocity, instead of relying upan diffusion connffted externally, but floats betwea, the olode ond effects. Thus, the&ift trmsistor can k ooemted at hiaher the sffond P region or external gate terminal (see figure frequencies th& the nmal junction transistor. ~ique~352 3-53). shows the impurity concentration grodient for o typical drift uansistor. It is also represmtative of the resistivity wadimt and the electric field ~roduced.which van in the ;we manner. Because of the.variable impurity distribution ANODE+dqkiHooE in (he hse regicn, less of the depletim arm extends into the he, and the total effect is that of widening the depletim arm. Shortino of the transistor by punch-throud- effect as the collector ;oltage is raised isehinated, because the depletion area will sraduallv extend into the Figure 3-53. base and coll&tor oreas, and blocks by the heavy Silicon Comtroll*d Rectifiet impurity mncmtration near the emitter region, limiting further sprmdto the collector region. At the same time, the The controlled rectifier is connected as a mnventimal strong elemic field produced by the varying resistivity rectifier with mode to positive mC cahde to negative. In qadimt from me md to the other of the transistor muses this condition, both end iunctions me forward-biased. but an aftraciim for the minority mniers ad thus urges injected the middle junction is reiersed-biased, ond only a sioli holes across the base region in the saw direction as the reverse current flows (conduction is effectively blaked). diffusion crurmts. 7he result is to provide o shoner When a positive gate is applied to the gate electrode, the transit time for the injected carriers than would nomlly middle junction is forwmd-biased md heavy current flows; occur for the sane base width if only the diffusion process or, when a specific blocking voltage is exceeded, the silicon were octing as o trrmspsrt medium. With a shorter transit mntmlled rectifier also brwks down ond operates exactly Ume, the hlgh-frequency response is extended aboue that of as if gated. Gnce conduction is initiated, it continues the mrml transistor. until either the current or the voltage drops below a small holding value or until the externol circuit is interrupted. Figure 2-51 shows o rypical circuit utilizing two cmtiolkd rectillers in a full-wave rectifier circuit. The output level EMITTER BASE COLLECTOR is deermined by the control circuit. llese units me op- erable over ranges of from 20 to 600 volts blocking and f P N P currents of 1 to over 100 amperes, under control of gates M4XIMUM from less than 1 volt or 1/4 milliampere to 3 to 4 volts at IUPURITY I CONCEMTRATION 1 I I 10 milliamperes, with turn-n time of 1 to 5 micmseconds I I I and tumdff times of 10 to M micmsemnds. I I I I I t ! DC TO FILTER TO CONTROL CIRCUIT -DISTANCE THROUGH TRIINSlSTOR - Fipr* 3-52. Figure 3-54, Drih Tmnriator Construction Controlled Rectifier Circuit ORIGINAL ELECTRONIC CIRUIITS NAVWIPS (00,M)ll. 102 SEMICONDUCTOR 3.6.3.9 ~h~totranslstor*.The phototmsistor is a emture chmaes like the photodiode. Humidity effectsare combinmion of two junction diodes orrmged as o conven- depmdent upthe cmstruction and encapsulation processes, tional transistor, for example, in o PNP configuration, but temperature wriotims may be commsated for by the with only the two end leads brought out. ?he mechanical use of a bridge circuit md a thermistor of equal but op- arrangement is such that light is focussed on either one or posite chmocteristics; see figure 3-57, both junctions to vary the conductivity of the unit. ?his unit is identical in operation to the photodiode, except th.ot it is mvch more sositive, from 50 to 5CE times, Mouse of tronsistor action. It is evident from fioure 355 that the connections are the some as for the photcdiode and that the emitter junction is reverspbiosed, with the collector iunnion forward biased ond the base ilmting. Biasing is achieved through the internal resistance of the junctions. The emitter is more ;,;j;l':.: :5c- :be CC!!P!CT. the hse floats somewhere in between, being at a lower positive porennai u~antiir collector, SO that it is e1lective:y rccasebi;sed {acs--in: a PNP unit). Since the base is truly !lw~nq(it is not :-....+ ....-+.,.".A tn mn,,nii throuqh LCT!I!CL?CY .-iil U," "i ll." ._>.._. the intemol hse-ernitter resistonmi, it is extremely sus- ceptible to any light impinging on the junction. Variations in light intensity couse the junction conductivity to vmy. and thus oct similmly to an input signal applied to a con- Figure 3-57. ventional emitter-base junction. Since the coiiector junc- Thermistor-Compensated Bridge Circuit tion is forwmd-biased, the cbongin: emitter cor~ductonce causes corresponding and amplified changes of collector 3.6.3.1 Thermlstor. A thenisto, is o swioi semi- current, developing an output acms load resistor Rr. conductor dedce wbch functions as a thermaliy sensitive Because of the large collector NrrRIt control offered resistor whose resistance vmies with temperature. 'herm- by the phototransistor, it may be used directly to con:rol istors have lmge negative temperature coefficients; that is. n relq connected to tun Dower on or off, or to operate a asthe temperature risestheir resistance decreases, ond as sait&irg drciit: see figur~3-%. the remperaturr bop5 t3-r ;ssi;x.n;; mL:x5es. ?:? resistance of o thermista is vmied not only by ambient !e-Fgtsre chmqoc b\)t01s" by ktamerated internally by the passole of cxrent. Since tine termistor is hiisi;;i!y c vcziable resistor, it 1s usuoiiy mnsuuctsd iron seii;iconductor material of KC!-te: recisti\.:!:. ear ?rIICP~ in transist~rsor serm- :onducrar diodes. Tne~nerrioie,its rispcrse :z s~.b:%! trmprat~rei;riut;sns does not track equa!ly with that of the tonsistor semiconductor, so that cmpensotim is cchiwed only at o few points of correspondence. As o iesc!!, 11s nrwrest usage is m thc fiell of tempersture contois mhmsurmmts, md powerneasuring eqlilp- ment based on heaung effect, such as I-: meosiirmg mc:? ucve eq~ip?m-+. Although it is a semiconductor. 11 has no ic::!zs!c ;-.-!i!imtinn mphillty like the transistor, md is -..-..--a-,~ ~ .- Vh.. ~ ~-nl>.";~ ;rim,,,,, i,,,;" Yncuje .; is u.ji: ln thsmoi conpe^iaImg CircJits ior riarsisior siib.i:iia";;.. 3.7 CLASSES OF AmPiiFiER OPERATION. . , x?rp rrnnqrrnrs are maluvvus ii VCC~,;:, ;"=a, .,-,c . . ss-e qmersi ?!asses ni onpiificatlon. ingut md output w," nercIs, &;x:;G-,, =-,< e:::cszz>: ze cppi :,.,. :,;-. -,"a the trans~storcon k uprrilica -5 9 Zios; A, .3;ss; 3, Class AE, or C!xs C r.ili!ier. Operating conditions and res~!ts!nithe !den1 rose ore used in the following dis- cussion to define tr.e 2iifetmies ail relationships Setv!~ toe rissses oi opmnon. ?.".: C!OISA. 7-r ?;us, A amplifier is biased so -t-" li. i,.,e,. 2-56. .'-.LL,". '. --"."wL."."" ..- =..- ni ,he L*;;niu, ,, ,~ Phototronrirtor Relay C"1,0, . " ...... ELECTRONIC CIRCUITS NAVWIPS SEMICONDUCTOR the tias point. Collector current flaws continuously than those of the CE c~rcuit. Therefore, hedistartim is (with or without sign00 for 350 degrees of the aperoting lower in the CB circuit thm in the CE circuit. Other cycle, and the transistor is operated so that the maximum parameters which affect the distortion produced ore: the collector dissipation is never exceeded (other classes cmplihlde of the input signal (if toa large, it will be mommtmily exceed this rating). clip~ed),the value and linearity of the input resistonce, 'The Class A amplifier is basically a small-sip4 and qprecloble variation of the bios with temperature. To amplifier, although it can be used as o large-signd minimize distortion md produce noximum gain, the CB amplifier provided that the quiescent current does not circuit uses or input resistance of abut two tlmes the exceed the maximum transistor ratings. Usuolly, large sowce impedance, while the CE circuit uses on input resist- signal amplifiers of the power Vpe ore operated os Class B ace one to thee times the murce impedmce, to minimize amplifius Class A amplifiers moy be operated ir. push- the over-all input resistance variations. Althoqh the CB pull a as single-ended stages. circuit produces less distortion and more power output for While the efficiency of o v~~um-tukeamplifier the same percentage distonion as the CE circuit, the CE operated Class A overages around 30 pecent, the efficiency circuit is usually preferred for oll wound use because it is of a tansistor operated Class A varies considembly, de- easily coxoded md has a high power gain. pending upon the circuit configuration md the parameters used. Considering the ideal case, it can be demonstroted mathmatically that the direct-coupled Class A onplifier produces a theoretical rmximum of 25 pwcent in either the CB a CE circuits. On the other hand, o resistance- coupled circuit will produce a maximum collector efficiency of 17 percent. The hiqhest~. possible efficienv.. 50 .oercent. is obtained with transformercoupled cmfiguration (assum. inq a perfect transformer, with no loss=), or by use of a shunt collmor feed. Fa Class A operation, the transistor must be capable of dissipating more than the desired power output. Figure 358 shows typical Closs A operation for o CB mfiguraticn, rmd figure 3-59, for a CE configuration. Note that operation does not extend into the saturation regim since the hee of the curve makes operation here very nonlinear. Likewise, operation h the cutoff reoion is not prmitted, because current would flow for less &an the entire cycle. Compming the graphs of figures 3.58 and 2-59, it is seen that the CB circuit is inherently more linear since the mnstontcumnt curves are more equally spaced Fipure 3-59. ~ .. .. - ----" CE Class A Graphical Operction IMAX LINE / LINE -R---- Ad,/; - 3.7.2 Class B. Class B amplifier opemtion is obtoin- ed when the collector cunect flows for one half of the operaling cycle, and is entirely cutoff during the other half. The bias is set at the ~toffpoint (zero bios), and during the positive input signal swing m NPN transistor will amplify in a normal fashion; on the negative swing the transistor is cut off md does not operote. A PNP tronsistor will conduct during the negative half cycle of the input signal and remain cut off during the positive swing. Tc produce the full input signal, two transistors must be emplayed, operating buck-toback in o psh-pull orrange- ment. On me half of the cycle one unit operates, on the other half cycle the other unit cperates, and the halves ore combined and added in the imd. %s each transistor operates for only half the operating period. Figure 360 shows o graph of Class B operation with the input and output signals prolected from the trmsfer characteristic. Note that while collector cutoff is assumed there is o small flow of reverse leakage current, ICEO,which reduces the total efficienq af the circuit. Figure 3-58. Ideal efficiency is 78 percent, which is quite an improve- CB Class A Graphical Operation ment over Class A operation. Distortim components are ORIGINAL ELECTRONIC ClRCUlTS NAVWIPS WO, WO. 102 SEMICONDUCTOR the meas for Closs A pius an additimal type, known as c.o..or.r di.tortion. Since two transistors ore employed. even though operating only half the time, the distortion is grwter than for Closs A depending on the circuit desiqa. At the present state of the art, no general figilies to indicate the ~ossiblerange of values oi distortin xeavailnbie. since to obtain the necessary gain or output it may be nec- essw la accept more distortion with me transistor ad design than with another. Because each transistor operates im only half the time and he power conversion efficiency is high, the Class B operated transistor is required to dissipate only abut 35 percmt of the total output power desired. Hence, much greater power output is pcssible with lower rated trrmsis- ICI Fiqure 3-61. Ctosror.r Distortion ibmpensouon tor crossover disroruon is usuuiiy uchieie: by piocing a siight iorward bias on the mse of the ;-a- sistor, to move the bias point to a more linear pJrtim of the trrmsfer characteristic. Wile feedkk mn be used or the swrce resistace can be !ncreased to minimize cross- over effects.circuit desian com~licatims,toaether with the lcss m the increased source resistmce, make these types of cmsotion aeneraliv unsatisfactorv. for cen~al- use. Actually, the biasingoif type of compensation picces the om~lifierin the Class AB rmae of ooemtion. '3.7.3 CIUSS AB. ~peroticiin th; class AB region is oetam& bf bIrnh5 to &; &:: -here .:c,;--:or --;;--t iiows famore than o nail qcie, ktnot ior u,e entire qrle an in CIoss A owration. By arrmging the bias properly, efficfencies between 50 and 78 percent are ob lainable, with an average of 55 perzrnt representhg typica! Class AB opaatlon. Ftwre 362 shows o arrph- . of tvotd Closs AB oeeio- tlon. sto onion :s less Lkthat ifClass 3 md moie Lhm hat of Qss A '!be cirait mrmwnmt is uaollv push- pull. However, far those ippllnniAs &I& cm &l&te Fipure 3-60. the increased distortion, it is possible to use singieended Tn!::l Closr 8 Opao?loc owrotion with an iacrease of output aver Class A operodor,. For pusbpull operation, Closs AB represents greater power tars for the Closs B mplifier. Since the ideal case is output md slightly more GIstortlor, thm iioss 4 lli'i less' USU&~ n~tabi;:-.ed, 5e ;ercen!qe to he &ssiFofPd pow6 oumut md sllqhtlv less distortion thm Clms K =hoz!d he --:-!cti.J i? +j.:L i~~:xce.kt the vs!:e .!"en 3.7.4 Clo.. C. Closs C aperatlcn is obtained by bias- ibve is o rough ~p~rmiu,;tis;. fsr ar;c;!sor. TiTSe?. 8.q m he plint rhar ,xli;;ectoi mi;^,: ncns :-:iezz ::=: Class B o~ctimis usually used fa mdio power a naii cycie, n'h hekoisistoi razdiing :; the -:sf! mpiiher siages, but is srbn employe2 s;sg!+er,?ec. ncnaum ma wm o siigni cutoii ;revase; mli;isii ::;n",, Howwer. sinsle-ended operation is applicable to Urmsmtt- durlng the inoperative portion oi the cycie. Ciass. . i opeiaaori ters using tank c!rc;i:s !o ti!! in !he ziss!~- kifni trip IS Ml use0 10; mQl0m>il;;ii~iT.-.l~;. kiai45c 2: ;.S 56iC.c output signal , as invacuum-take operalion. distortion it produces. it is used iar tmi; orair wpiicnlma Crossover dlstoruon is c~usedhisiaily kq the noir- %ere 3e &smruon :E smoolhd ,JUL md ~n~i~i~~ii2:b. t:i . ~~ lineaity ofthe transistor charanerfstlcs. Ar smaii lnpur ii","Qeel er;&-:, os j~ .,nz>;mpd& spep2e&;;,&>, i<:s wltqes the wrent change is small and varies exmen- used tn dnale-ended or wsh-pull mnfiwotionr Switctilna " ' L.A- l- .La ..mc,ctn, -,i,,",im -. . -... ~ ~~~~ ,,u,,y, "A, u,,uy,-- U,,,", ,".."3-" ".b " drarlts are-usldlv ope&& Closs c mplifiers is hmvier md heavier. This action proiuces an inward To achieve Class C meratirr. with a his rain! cm- belly, as show, I.? figure 3-51, wd !ncreasd dtstat~m. sidaably Mo* cutoff, it is neceswny to reversebias the emitter (ossiimhi c ;:aa7ion-en:tter circw!!, os op~osea 9 !orrmd-n!~ i~rmrmqi "perorion in he uii~iiustj. ORIGINAL ELECTRONIC CIRCUITS NAVWIPS 9ao.oOO.IW SEMICONDUCTOR sary to supply the losses in the tuned inbctor by trmsistor conduction, md obtdn m amplified sine wave output pro- bced b/ the voltoge gain fonor. Naturally this type of operatim is restricted to essentially sine-wave oscillations pmduced at the frequency to which the tuned load cirmit is remwt. Figure 3-63 shows a typical Class C amplifier drcuit with input md outwt waveforms. 3.8 COUPLING METHODS. 'he trmsistor, like the vacuum tube, is usually mn- nected in cascaded stages to mnplify the feeble input signd to the large outpt value needed Coupling is oc- mmplished by using resistancecapacitance networks, impdmce networks, or transformers, or directly, by cm- necting the output element to the input element of the suc- ceeding stage, as derribed in the following pmographs. The discussion in this mion will be limited to the basic circult md importmt mnsiderations inmlved for mdio or rdatlvely low-frequency circuits mere special mmbindions or design mnsidaations are required to achieve a porticulm result (for exanple, r-f or i-1 coupling), they will be dis- assed in the prcper sectlon with the special circult with which they me used. Since all coupling networks me frequency responsive to a certain extent, some mupling methods offord better results thm others for a parn~~lar Fipun 3-62. drmit configuration. Generally spwking, resistmce Tvical Cloar AB Push-Pull Op.mtion coupling affords a wide frequency response with economy of pons and full trmsistor gain cwabiiities, impedwce The Class C mplifler cm be ansidered to wmte as a and hsformer coupling provide a more efficient power pulsed osdllatnr for 1-1 energy, where the input pulses matching cwability with moderate frequency respnse, cmse andrctlon for a andl portion of the operating cyde, while direct mupling provides the maximum economy of pans md the 6mslstor rests with a small steodv mnmt durino with excellent low-hequmcy response wd d-c mpliUcdon. me mn&der of the cyde, in o cutoff mdition, with the 3.8.1 R-C bupiinp. The RC coupler utilizes two re- 1-1 osd~atbnsbelnq sust&d a, the paallel resonant sistors md a crpacitor to form m interstage mupling device tmk dmlt As~unlngm input sine wave, it is only neces- which provides a brood hequmcy rewnse, with high gain, M economy of parts, md snall physical size. It is used extmsively in mdio mplifiers, pmticulmly in the low- level stages. Becmse of its poor input-output power mn- case), version efficienm. (17. r~oercent for the ideal it is -++- seldom used in power output stages. 'in 'b Ic %no Fiaure 3-54 shows a typical resistmce coupler. Resistor OUT RL is the collector load resistor for the first stags, capacitor Ccc is the d-c voltogeblocking and a-c signal-coupling capacitor, and RB is the input-load and dc-return resistor for the baseemitter junction of the semnd stage. Figure 3-63. Figwe 3-64. Cloaa C Amplifier, CE Circuit Rerialance Coupling ORIGINAL ELECTRONIC CIRCUITS HAVWIPS 900,WO.lM SEMICOWDUCTOR Slnce the input resistance of the second stage is low (onthe order of 1WO ohms for a CE cirait) md the reactance of the mupling cqacitor is in series with the base-emitter internal input resistance, Ccc must have a low reactance to minimize low-hequency ottenumim due to a large signal dmp amass the mupiing cqocitor. This is adiwed by using a high value of capacitance: thus, for low mdio fre- quencies, vaiues of ihio :~b.T.;c;;f^.ds or mnre nl? em- ployed (mmpare this with the voaum-iuk mupling c~adt- mce of less thm i mictoiarodl. To prevent kunting the input signal mnd the low baseemitter lnput resistmce, the base dc return resistor. As, is mode os large as practical with respect to the uan- sistor input resistonce. Since increasing the base series resistmce deteriorates the temperature stability of the hse junction (see dwussion of bios stabli1~atlmin ?UIU~L&, 2.4.21, tbr vdue selected for the input resistor is o com- promise between redudng the effectiveshunting of the inwt resistmce md mainlolninq wifficimt thermal stability o;er the the desired tempermur; rmgr oi opeirdiicfi. The hlch-treareno rewmse is normallv IirJted bv me SU~cirCU~t cq;citance P~JSme inpJt ndoutp~tciarl- tmce: hence. !he cmslstor itself is dsrallv be limit~?a foctor. The low-frequency respse is normally limitedby the time constant of the coupling capacitor, Ccc, and the base return (input) resistmce, Rs. For gmd low-irequmcy respcnse, the time mnstmt must be long in mmporison to the lowest fre~enqto be anplified Like the vwum-tube coupling networks, trmslstor mupllng networks muy also be mmpmsated to hcrease irequenq rrgianse. Fi;ji;r M5 zk.j.*.j tLe kSc y!~!w- lent cirdts ior three types of mmpensotion: (A) i;mt p-&lnq !B! series pwkina, md (0mmblned shunt-series peding. Insertion of series inductor LI produces a parallel resonont efien with output capacitance C,. and input capacitance CL. and improves the high-frequenq response about 9 percent. Inserticn of inductor L2 in series with Ccc produces a series rescnant circuit with Input capocit- Figurn 3-65. once Ci. and further increases the hlgh-frequency respcmse Sbsmt, kr(*a, and Combined Psaklnp Circuits hut 3 DelCmt OVS thOl Of &~tpwkhg. 'JShg k0lh series- and kunt-peoklng effms pmvides a gain &ul 50 percent gmtei than that of the series-pmking circuit alone. Slnce the tespmse to low kequmdes is limited only by ih.e cmplinq network. low-frequmr, compmsoflon can be zmvtdd 2s Ln wolum-tube circuits. Figure % shows . . a typical iow-frquency compensaiim clrca:. Wit? :esisloi H: inserted in series wlth iir, the collector load is Lqcteased at those hequmcies !or wn~cnthe resisrmxt sf ?., :s effective. Since capacitor Ci paralleis or shunts 31,it is evident that the haer irequenitrs ae $pi;ssc-2 =ox.' ifr but, since the capacitive reactance of CI increases with o decrease oi i:qm;y, he ioww frquer,des pasc thmgh 31. Thus, the iwd resistG~cefc: !ow fiqacies is in- creased md s, is the output at these hewencier The =zLL?c'lm nf C: and RI is chosen to pmvide the desired frwmcy mnmsotim. ?his type of cornpensouon oln, corrects for phase distortim, which is usually more prevalent ot the lower irequmdes 3.2.2 :zp;dnes te.9img. The im~dm,~ec3dpier is . . . . us- enenslveq iii uic iw,;i;:;: f:::?. !!-- -*- :-crws?d ORIGINAL ELECTRONIC URWlTS NAVSHIPS ~,000.102 SEMICONDUCTOR pown-hmdlinq (ond mo:aiinq) cqobilities nl the inductor mmponmts, but it mmpores fowrzbly in these respects with provide moie a~tputthan ;he lood resistor. Wt,lle the ver- the impedmce wupier. Its frequmw respcnse is less than all frequenq response cf imprdmce mupiing s n-;t os thot of tkte ;esistmce- or impedance-mupled circuit. good os thcl of resistance 73.2~.!!1~,ii is rnhkitel :?:m Figure %8 bows a typical transforma mupier. that of transformer coup:inq, i~c3115ethne ee n- iss.qc Cowling k!rm stsges is achieved through the mutual remmce effects to de~eiioimet~e hi$-i:i.juaq response. inductive coupling of prirnoly and secondary windings. Part A 01 Uguie 3-67 siaws the basic impedance- r:oupl- Since these nindinjs ore separated physically, the input ad inq drarit, and Pmt B shows 3 qpicd vmiotion. Thi ou?pbt circuits ore isdated for d-c biasing, yet mupled for high-frequmq'responsr oi the impdmce aupier is limi.ei a-c simd timsfer. The primory winding presents a low mainlv. b/ . the mllector outaut cmacitmce. anc the low- d-c resistm;e, minimizing milector current losses md frequency ieiponse is limCL& bi the *un! reoc:mce of the dlow~ogo lower qplied mllector voltoge for the same gain inductor, L1. The effidacy of ?he imoedmce mu~leris as other wupling methods, md it presents m a-c lood im- qproxlmately the sane as t$a! of the tims'oimer-cdp!ed pedmce which includes the reflected input (boseemitts) circuit (53 percent for the ideal cose). impedance oi the following stage. The semdaty winding also completes the base d-c return path and provides better thermal stability because of the law d-c (widing) resistmce. Since 'he trmsistor input md output impedoice cm be matched by usina the proper turns ratio, maximum available gain cm be obtained from the umsistor. As in tie impedance coupler, the &unt reanmce of the trmsformei win0ings causes the low-frequmq response to drop off, whiie hi&-freq~encfresponse is limited hy the lmkqe reactmce between the primary ond secondary wmdings, in additim to the effectof mllector capocitmce. Becn~useof rtie low sl-c resistance in the primcoy winding, no excess power is dissipated, md he pvfa eificimq ap- pmades the maximun thmreticd value of 50 percent. 3.5.4 Dine bupllng. Direct couplinq is used for amplification of dc md very low trqmcies. As in vacuum- Puke nrcuits. this methud of coupling is limited to a few Figure 3-68. Tronsfomsr Coupling L-C-R COUPLING stages since dl 2iwals ore amplified, including noise, old it is extremely susceptible to instability becplse of shift of operating point, cumulative d-c drift, md thermal chmges. Its use in power output stages is limited because of the low mversiw, effidenq (about 25 percent). It does offer on economy of ports, adit lends itself to the use of cwnple- mmtmy-symmetry circuitry. Figure 369 shows o basic &c m~plifierutilizing two PNP trmssors and two pcwer souzces. When a signol is 3.8.3 Tmnabnn-r Ceupllns. Transformer coupling is applied to the base oi 91, the amplified output is directly used extensively in caxoded 1:msistar stages md power cpplim to the base of 02 Oom the mllector of 01. 'The ougot stoges It provides wdhequenq response and output is token from load resistor RL of 92. Since the Proper matching of inpui and output iesistmces with qmd base bias of 92 is cpplied through Rs2, the amplified sip power conversion efficiency. It is relatively much more nd on the collector of Ql must not drive the base of 92 posi- costly mid ocrupies more space thm the simpie P-C circuit tive; thot is, it must no! exceed the neqdve bias. ELECTRONIC CIRCUITS NAVWIPS poo.ooo.102 SEMICONDUCTOR Note the use of complementmy symmetry or the use of OUT one uansistor to bias mother with d-c mapling affords the miminum of component parts pssible, adrepresents m etonouic advantage that is possible only with transistors. Ftgure 3-69, D-C rmpiiisrr Figure 3-71. Figure 3-70 shows o bodi connecion not possible ComplcmsntarySymm&ty D-C Amplifier with electron-?-be mplifiers. 'he grounded-bose circuit of Ql is directmected to the grounded-emltter circuit Spxio; bias circuits ore used with &c amplifiers to of Q2. 'Ihus the input circuit of P2 is the load for 3!, on0 reduae thermal effects;see has staSi!ization discussion mllectar bins for 01 is obtained thrwqh the mliecior-to- in poragaphs 2.2 ond 3.4 for basic cirmiuy. base junctim of Q2. Since Q2 biases Ql,only one powe source is needed. 3.9 TIME COHSTANTS. The time constont as defined in paragraph 2.5 for e!e?mr hlbs isthe same !or transistors. It is imprtmt -I:-- 4.". tmni-i~tnr; 'i!fn- .-.u :+i.,~i- uar " "...- 3 'rlrJiiiy frox electron tubes in their inydt and outout :esistances and their c3- pocltu~ces. i,ne;e rize cons:m:s ore .r ;he ;;i? circait oi an electron tube wllh essentialiy infinite input impdmce, it is not ntxessory to be cmcerned with 'he input-impedance effect on the time constant. Since the rronsisror bas ctinite ond reiative!y low input in&a:se, however, it moy affect o timeconstant circuit. Also, the ;:;nd!nce to hse of the transistor is usually iarqer than , " ! .- ,.",." u. ...id ?""",-"rn"~. hw,;~,*her :t sTc.:s :'ie :i:ec~~stcn.! ~iic~i!,it -;rc: be Figure 3-76. consider&. m L; L& -.h"* U~,.' CB to CE DC Ampiiiiar -=, --e.. . . . ?r+! I-" r!rcuits use4 for timedelay, coupling, ond hequenq-respnse effects ond Fiq~re3-71 shows a ~picalmmplenmtary-symmet~ tor the shaplnq oi pulses on6 &e vilniti:;Lty ' 7.&:c'hiz; 7z ,:a T.:-A!,2sl,?q g, \<2i<<,r,,; ,J P:;? trx,si;:~:. -7.x ::c :::. ,.,~,.,,, -. y,r,>,-;~i,:::;;.",,,:3:c:,z-.=s=yi.z :=:~.=:; : i!~..!,::?.!ir!,: rents !iow IP. opposiie iiiectiiiris, tli.mliil if:a-:~ .F;CSI ~jf??~)k,Lv?rn eiec?1,2n-l"~&ci;c"ils "..i :.2..5::::: adstotilize ~chomer, As ~n uguie >YE, C-.e -:!:eL::...... bias for Ql is obtained from fie base-coiieclor ]unction -iransien! cm~di20~swhich prcduce irrge oveisi~cois "i 77 - -.-"* "-2. :.. ,.--.'.,,.,~ . . ;:r~~. i:; iff2;:SP:te t'nsis. .. , Fmthe circuit of figure 3-71, it is clmrly seen :not (01 IflXe ~GS~A,dG,;dGcC XZ,::A <.zb;.~~ :..k>,) ?C, if or&,er stq.were 33de5 T O<~;!:MIU: UII~iiiisii iii!!ircc: .--.:-I- constant circuitry will be completely discussed in the tmeous equotims in which the h-parameters are the applicable circuit malvsis in other sections of this tech- coefficients, namely: nical manual, since it depends primarily on the type of tran- ~ ...... sistor selected. Iz = hz1 i, t ~ZZEZ To conform with Kirchhoff's laws, hll in fiaure 3-728 . ~ 3.10 HYBRID PARAMETERS. must be an impedance and hzz an odmittance, while hlz The hybrid parameters, or h-parameters, of the transis- and h21 are essentiollv dimensionless ratios. For Low tor are mostly of use tothe circuit desiqer. However, frequ~lcieshli and hzl ore resistive. Since these para- manufacturers have found them convenimt for use in meters involve two opposites-impedance md admittmce- defining the performmce of their products. 'Iberefore, o the term hybrid is used to describe them. working knowledge of the use and meaning of h-pameters is essential to the technician. The h-parameters appear in two forms which are inter- changeable; one form employs letter subscripts, and the other, numerical subscripts. At present, the numerical subscripts are commonly used for general circuit analysis. and the letter subscripts are used for specifiying character- istics of transistors. Industry standardization accepts both forms, htthe present trend in usage indicates that -the nu- rneriml subsniots mw. be .ureferred. In addition. there are other systems of parameters, such os "a". "b". "y", "q", "r", and "z" parameters, which have somewhat more specialized uses. All of these systems, which may seem confusing to myone otherthan a trained engineer, represent different methods of mathematically defining transistor actim, as well as the parameters limiting tho1 action, for GEN design pwpses. Although the triode trmsistor is o 5 "21 il terminal device, it may be treated as a "black box" with two input md two output connections ( a basic Cterminai network). By utilizing the electrical characteristics (h- parameters) of this black box, it is possible to calculate perfammce of various circuits when various input signals are applied.. and various loads are connected. Bosicallv... these h-parameters are limited to frequencies sufficiently Figwe 3-72. low (270-10W cps) that thecapacitive and inductive Tronristor ond FourTerminal Network Equivalent Circuit effects of the transistor can be neglected. The h-parameters for common-base connection are usually show in specifica- If the output terminals me shmt4rcuited for ac tion sheets because the emitter current md collectar volt- (by a large capacitor), the output voltaqe (ez) is age can be maintained more precisely than for other mnfiv zero, md the following simple formulas (like Ohm's uratims. Because of the trend toward the use of cammon- law) show the relationships between input voltoge md cmltter clrnlts md tke rel2tiv? e:se ol measuremmt, sane current and between input current and output cunent. ZE n-prlmeter,r- rill clso E crservei. Ir my evmt, fnzulas are woilable for conversion from one mfiguration to the the dher in most text bmks (and transistor manuals), so only the common-base connection will be discussed in this manuol. The simple canmoll-base configuratim shown in figure 3-72A can be represented hv the four-terminal h-parameter equivalent circuit of fiqure 3-728. In using the h-parameters, If the os input circuit is opened by the insertion of it is customarv. to iqnore- the bias and consider mlv the a luge inductance in series with the bios, therebl r&cing instmtaneous osvalues involved. Thus, the h-parameters i, to zero, the followinq additional formulas will be obtained: reuresmt owratinq conditions for a small sianal close to the operating point. Therefore, the equivalent circuits do h, h, = and h, = 4 not show bias supplies and polarities. Convmtimal currents -$ E, (not electron flow) and voltaqe polarities me assumed, and if errmeously assigned, will result in a negative answer 'ihus, h 1 r is effectively the transistor input impedmce when the problem is solved. Since the circuit of figure (with the output short-circuited), and hzz is the output 3-72 is essmtiolly a four-terminal netwrk (two input and admittance (with the input opensircuited). Similarly, h, two output terminals), it cm be described by two simul- is the wltqe feedback ratio with the input open-drmited (this represents the internal feedback due to reversffurrmt effectsand common impedmce coupling within the trmsis ORIGINAL ELECTRONIC CIRCUITS NAVWIPS SEMICONDUCTOR tor). Porometer hzi is the forword current arnpliii;st~on parameter designations hL h, hi, and ho with the additional ratio with the output short-circui!ed sibscript b, e, or c added to represent the common base, The functioning of the wuivoint circuit md the xeaning witter, or mllector configuration, respectively. The letter of the h-parmeters cm perhaps be more clearly understood and numerical forms of the parameters are related as follows: by considering the following intuitive reasaning. Consider hi is hll, h, is hlz, hr is hzi, and h. is h22. the c~rmitof figure 3-72E, md io! Lhe rfiomen: neglect :h2 Froiii the precedining dismssion, it is obvious tho1 with voltooe produced 'by tie ,ioitage ?ene:otm (L~;EN; i:! tile a few external measurements the h-parameters of the typico! mput circuit. 'Wen the input siynol voltrrqe (E,: is s;clied "black tor'' cm ce determmed, wd inoi subsiiiuiiuti uf to the input terminals, current il fiouis thrc~ghicsistli these volues in the proper formulas will allow cirmit hi 1 and causes curen: h21 ii :o f!cv in :he 2;l:;;t ?-r:r?! performmce to be approdmoted so thal the proper maiching source (current generator IGENin the fig~~rei.Thus, b.:: is values of external circuitry con be chosen by the designer. the currmt goin of the equivalent circuit. C-rre-t "1: i I divides betweer. the ouput :esis:::, rhck :s aq.m! :ri Yh22 (hzz is an admittance), and thc exterr.al circ-itv coxne-te4 ..--=.--.--. 'ha.... *rnncictn. nlltnii, !~rw\?ni~.T-a ..-3l:^:e across the output os o result 01 tnis currmr 1s me OUYIUL \ voitoqe \~2,. %en vu:luqc Lz ;;pi-jis ~;:c;; z;!~.;!, it cmses m. Lr:e:nzi !wL.-d. :::-;t :: .I ':? 3:-x '-,, '-:', .... .iir .-l.r"o i" i.. ~.,',...... , ,.,.- .u..uub... ,,,,, r; r COMMON COLLECTOR ORIGINAL