Freescale Semiconductor, Inc... ARCHIVE INFORMATION 33333 MOTOROLA SEMICONDUCTOR APPLICATION NOTE INTRODUCTION HelgeGranberg Prepared by: A 28V, 160WAMPLIFIER 2 and3.Two2 2N5942transistors areemployedinthedesign. in theschematicdiagramofFigure 1andphotosofFigures Ω downtime fortransistorreplacements. important inmostequipmentdesignstoavoidpossible any apparentdamagetoofthetransistors.Thisisvery mismatches forseveralminutesatfullpowerlevels without amplifiers were subjectedtoopenandshortcircuitoutput minutes, acoolingfanshouldbeprovided. exceed morethanaduration ofafew to is testing bench is some15dBbelowpeaklevels.However, if two–tone conditions, sincewithspeechoperationtheaverage power these heat-sinks,coolingfansarenotrequiredfornormal uses aheat-sinkwith1.40 characteristic of0.85 thermal operation. The28Vamplifierrequiresaheat-sinkwith amplifier requiressomeamountofheat-sinkingfor proper stage toprovideatotalpowergainofabout30dB.Each Both designscoverthe3–30MHzbandandutilizeadriver from a28Vlineanditisintendedforfixlocationsystems. power sources.Theothersupplies160Wwhenoperated mobile communicationssystemsoperatingfroma12.5V in thisApplicationNote.The80Watt designisintendedfor designs. it isalsorequiredtoalesserdegreeinparalleltransistor matching howeverisnotlimitedtopush-pull circuitssince designs issuperiortothatofsingle-endedcircuits.Device even intheworstcasesuppressionprovidedpush-pull the matchingbetweentwooutputdevices.Nevertheless, dependent onseveralfactors,themostsignificantonebeing suppression available with push-pull stagesis highly it thebetterchoice.Theexactamountofeven-harmonic mode offers improvedeven-harmonicsuppressionmaking can oftenmeetthepoweroutputdemands,push-pull configuration isoftenemployed.Althoughparalleloperation achieved with a single transistor, a push-pull output and toattainhigherpowerlevelsthancanbegenerally Tohigh-powerstages. meetthesedistortion requirements transmitters, placesstringentdistortion requirements on the USING PUSH-PULLTRANSISTORS BROADBAND LINEARPOWERAMPLIFIERS  RF Application Reports RF Application load with IMD performance of – 30 dB or betterisshown loadwithIMDperformanceof –30dB Motorola, Inc.1993 An amplifierwhichcansupply 160watts(PEP) into a 50 Toof both engineeringmodels ruggedness, assure Two linearpoweramplifierdesignsaretobediscussed Linear power amplifier operation, as used in SSB RF CircuitsEngineering ° ° C/W thermalresistance.With C/W whilethe12.5Vversion Freescale Semiconductor,Inc.

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n t f o o : r w m w a t w i o . f n r e output anddriverdevices.Thiscontrolisalsousefulifthe the idlingcurrentforboth of control adjustmentallows to compensateforvariationsintransistorcurrentgain.This more significantthanthefifthorderproducts. lower powerlevels.Generally, thirdorderdistortionismuch but willhavelittleeffect onthirdorderproductsexceptat quiescent currentlevelswillreducefifthorderIMDproducts, of 60–80mAforeachtransistorshouldbeprovided.Higher For broadbandlinearoperation,aquiescentcollectorcurrent intermodulation distortionproducts (IMD)ratedat–30dB. These transistorsarespecifiedat80watts(PEP)outputwith a singlefrequencytestand80wattsaverageoutput. in theoutputtransistorparameters.Thisdatawastakenwith harmonic suppressionwhichisdegradedbythemismatch chosen 2N5942transistors.Table 1showsthemeasured “similar” pairswereselectedfromatotaloftenrandomly model used,thetransistorswerenotperfectlymatched. Four effective cancellationofevenharmonics.Intheengineering is necessarysincebroad-bandoperationrequires more require morestringentlimitsifbroad-banding may matching frequency shouldbematchedwithinabout15–20%.This design, bothdccurrentgainandpower at a midband outputtransistorsbebetamatched.As withanypush-pull the amplifier isoperatedfromasupplyotherthan28volts. efficiency. current levelswillnotimprove linearity, butwilldegradedriver IMD performancewiththe2N6370. Higher best provides A quiescentcollectorcurrent levelofatleast10–15mA IMD istypicallybetterthan– 40dBwithClassBbiasing. maximum necessaryto drive two2N5942transistors,the However, atabout4.5W(PEP)output,whichisthe is specified–30dBIMDwhendelivering10watts(PEP). O Table 1.HarmonicSuppressionof28VAmplifieratFull Frequency Harmonic e n A biasingadjustmentisprovidedintheamplifiercircuit Even withthebiasingcontrol,itisstronglysuggestedthat A 2N6370transistorisemployedasadriver. Thisdevice s c T a h l i e s . c P 30 MHz 12 MHz o r 6 MHz 3 MHz o m d u c t , – 35dB – 16dB – 15dB – 16dB Output Power 2nd – 20dB – 24dB – 20dB – 30dB 3rd Order thisdocument – 51dB – 22dB – 21dB – 22dB 4th AN593 by AN593/D – 44dB – 34dB – 37dB – 37dB 5th 1 PRODUCT TRANSFERRED TO M/A–COM

Freescale Semiconductor, Inc... R5, R6 R4 R3 R2 R1 C23 C20 C18, C19,C21 C17 C13, C14 C2, C3 R12 R10 R9, R11 R7, R8 ARCHIVEC11, C12 C9, C10,C15,C22 C8 INFC6 C5, C7,C16 C4 C1 ORMATION 2 — — — — — — — — divided equallybetweenbothemitterleads) — — — — — 620pFdippedmica 820 220 500 100 35 47 0.033 0.85 1k,1/2Wpotentiometer 10 0.1 0.1 — — — — Ω Ω 0.01 10 Two 150 — — Ω Ω µ µ µ 1k,1/2Wcarbon , 5Wwire , 1/2Wcarbon µ µ F/35 Velectrolytic F/6 Velectrolytic F/15 Velectrolytic 0.01 , 1Wwire , 1/4Wcarbon 0.015 Ω µ F discceramic F discceramic — Ω F mylar , (65.1 , 1/2Wcarbon 0.1 µ — F mylar Two 0.068 µ F µ — Ω µ F mylar F ceramic Ω , 1/2Wcarboninparallel 1000pFfeedthrough or43.3 µ F mylarsinparallel Ω 1/4 resistors inparallel, Freescale Semiconductor,Inc.

Figure 1.160Watt (PEP)Broadband LinearAmplifier F o

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w m AN593 w a t w i o T4 T3 T2 T1 . f n L8, L9 L4, L5 L3 L2, L6,L7 L1 r — — — — e O — — e wire (Allwindings6twistsperinch).(T4 of #24AWG, C 1:4 Transformer Balun,A&B enameled wire(6twistsperinch) Collector choke,4turns,2twistedpairsof#22AWG enameled wire(6twistsperinch) 1:1 Balun,6turns,2twistedpairsof#24AWG enameled wire(8twistsperinch) 4:1 Transformer, 6turns,2twistedpairsof#26AWG F627-8Q1 ferritetoroidsorequivalent.) General F624-19Q1 n 1.8 .33 s

— — c T .22 3ferritebeadseach a h µ µ — H, (Ohmite2-144) H, moldedchoke l i e s 10 µ .

H, moldedchoke c P µ o r H, moldedchoke o m — d u 8turns,1twistedpairof#24AWG enameled PARTS LIST c — t AllothersareIndianaGeneral , — 5turns,2twistedpairs RF Application Reports RF Application J1, J2 D2 D1 Q4 Q2, Q3 Q1

— — — — — 1N4997 1N4001 2N5190 2N6370 Indiana — — BNCconnectors 2N5942

PRODUCT TRANSFERRED TO M/A–COM

Freescale Semiconductor, Inc... ARCHIVE INFORMATION RF Application Reports RF Application Two twisted Figure 2.Photoof28VLinearAmplifier pairs C Pair Pair #1 Unbalanced Input 50 Pair #2 Ω Freescale Semiconductor,Inc. Figure 4.Transformer Detailsfor28VLinearAmplifier To basesof

transistors T4 F o

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n B t f o o : Twisted r w m pair AN593 w Pairs a Balanced 12.5 t w i o . f Ω n r e O e Figure 3.PhotoofBackSide28VLinearAmplifier n s NOTE: Picturesdonotindicateactualnumberofturns. although notshownhere. Multiple linetransformersmustbewoundbifilarly, c T a h l i e s . c P 50 o r o m Ω Pairs d u c t Pairs , T1 12.5 Ω 3 PRODUCT TRANSFERRED TO M/A–COM

Freescale Semiconductor, Inc... ARCHIVE INFORMATION prototype amplifierovera3 variation of0.5dBwasmeasuredonanengineering shown intheschematicdiagram,Figure1,atotalgain driver stage.Withthisfeedbackandthenetworks feedback isintroducedinthefinalstageand15dB of thedesiredfrequencyband,approximately4.5dB on boththefinalamplifieranddriverstages.Atlowend operating frequency, negativevoltagefeedbackis employed Feedback unit withthreeseparatewindings. end. Again bothwiresofeachpairaresolderedtogetherat Figure 4 eachofthepairsistreatedasasinglewire. two-twisted pairsofwire(fourwirestotal).Asshownin with twodifferent colorsofinsulation. 4. Thepairscaneasilybeidentifiedbychoosingwires Figure Each pairthusconnectedisshownasasinglewirein from eachoriginalpairaresolderedtogetheratend. (four separatewires),aretwistedtogetherandthetwowires two twistedpairswoundonatoroidalcore.The at thebaseofQ1.Thistransformerconsistssixturns matchthe50 to transformers willfollow. in the references. A short description of each of the Additional informationonthesetransformerscanbefound T2 andT3haveturnratiosof4:1,1:11:4respectively. twisted-pair windingsandtoroidalcores.Transformers T1, coupling andsignal-splitting.Thesetransformersutilize for employed were transformers line-type transmission Transformers Employed evaluation waslessthan1.5dB. differential for inconstructed three identical amplifiers The fluxdensitymaybecomputed fromequation1. has aspecifiedmaximumflux densityofabout100gauss. 10 many turnsastwistedpairsaA andbB. Deviations of about From this,windingcC(atwistedpair)shouldhavetwiceas c andCshouldbeequaltothevoltageacrosswindingsDE. of T4,itcanbeseenthatthesumvoltagesacross although forsimplicitythefiguresdonotshowthis. in Figure4.Thethreewindings arebifilarwound, shown formed fromeightturnsofasinglepair. Connectionsare b consistof5turnstwotwistedpairswhileCandcare from thewindingitisconnectedto.WindingsA,a,Band A andBwhilethegroundedlineisin the opposite direction output lineofthebalunisinsamedirectionaswindings capital andlowercaseletters(i.e.windingsAa).The windings inasingletwistedpairareindicatedbysimilar diagram oftransformerT4isshowninFigure5.Thetwo 4 To compensateforvariationsinoutputwithchanges The ferritecoreusedforT4 in thepartslistofFigure1 Referring toFigure5theequivalentconnectiondiagram A lumped-constantequivalentconventionaltransformer Transformer T4 Transformer T3 Transformer T2 Transformer T1 In ordertoachievethedesiredbroadbandresponse, – 20%fromthe2:1ratiodonot produce noticeableef Ω sourcetothelowimpedancelevelrequired consistsoffourturnstwotwistedpairs. isa1:1Balunconsistingofsixturns providesanimpedancetransformation is a 1:4ratiounbalancedtobalanced is – 30MHzrange.Thetotalgain Freescale Semiconductor,Inc.

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n t f o o : fects. r w m AN593 w a t w i o . f n r e therefore: hr V=RMSvoltageacrossthewinding89 V where 28 V 160Watt (PEP)amplifier. measurement performedonanengineeringmodelofthe Amplifier Performance O e

n The datashowninthefollowingcurveswasobtainedfrom The Despite thisslightoverrating,densityisnotexcessive. s Figure 5.EquivalentLumpedElementFormofT4 c

T Figure 6.IMDasaFunction ofOutputPower a h .4=2 4.44 A = crosssectionalareaofToroid = inCm A =numberofturns(windingsAaandBbonly. n =frequencyinHertz3x10 f l i e s Bmax = .

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for 28VAmplifier t , 89 x10 4.44 fnA V x10 6 ) 20(.25) 8

RF Application Reports RF Application 8

gauss

= 133gauss 6 2 =0.25 (1) PRODUCT TRANSFERRED TO M/A–COM

Freescale Semiconductor, Inc... ARCHIVE INFORMATION Figure 7.OutputPowerfor

RF Application Reports RF Application

Figure 9.PowerGainversus Frequency

Figure 8.IMDversusFrequency

V

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for28VAmplifier – 30dBIMDasaFunctionof

Freescale Semiconductor,Inc.

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w m AN593 w a t w i o . f n r e AN 80WATT (PEP)12.5 IMD, devices areratedat40Watts (PEP)and of thetransmitterdesignina push-pull configuration. These in broadbandoperation. increasing thisto40mAyieldedsomewhatbetterlinearity quiescent collectorcurrentof35mA,butitwasfoundthat to betterthan40dB.The2N6367datasheetsuggests a the 2 At loweroperatingfrequencies,driverequirementsdropto with aresultingIMDperformanceofabout design thedrivermustsupplyonly5watts(PEP)at30MHz isspecifiedforupto9watts(PEP)output.Intheamplifier and transistors. The2N6367transistorisemployedasadriver 12, 13and14.Itutilizesa2N6367pairof2N6368 andevaluated.ThisamplifierisshowninFigures constructed a second amplifier designed for 12 V operation was was usedinthisdesignforimproved linearity. current l band operation. O e n Twoare employedinthefinalstage transistors 2N6368 To complementthe28Voltpreviously,discussed amplifier The 2N6368datasheetsuggests aquiescentcollector s

c T although – Figure 10.Total EfficiencyversusFrequency a h 3Watt (PEP)rangeandIMDperformanceimproves l evel of50mA,butalevel60 mAforeachtransistor i e s

.

Figure 11. VSWRversusFrequency c

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– 30dBmaximum – 37to – 38dB. 5 PRODUCT TRANSFERRED TO M/A–COM

Freescale Semiconductor, Inc... ARCHIVE INFORMATION C8, C9 C11, C12 C10 C5 C4, C6 C3 C1, C14,C18 C15 C2, C7,C13,C20 R10 R8, R9 R4, R5 R3 R2 R1, R6,R7 C26 C25 C24 C23 C21, C22 C19 C16, C17 6 — — — — — — — — — — — — 0.0047 100 240 51 1000 10pF15V 470pFmica 33 680pFmica 330pFmica .01 39pFmica — — — — Ω 0.015and0.033 0.033 27 18 — — — µ Ω Ω , 1/2Wcarbon µ — F/3 V 560pFmica , 6Wwire , 1wireW 0.015 Two 0.068 F ceramic µ Ω Ω µ 10 — F/3 V F mylar , 2Wcarbon , 1Wcarbon 0.1 µ Ω F mylar — µ , 1/2Wcarbon F mylar 0.001 µ F ceramic µ F mylarsinparallel µ µ F mylarsinparallel F feedthrough Freescale Semiconductor,Inc.

F Figure 12.SchematicDiagramof12.5VAmplifier o

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n t f o o : r w m AN593 w a t w i o . f n J1, J2 D2 D1 Q2, Q3 Q1 T4 T3 T2 T1 L4, L9 L3 L5, L6 L2, L7,L8 L1 r e O — — — — — — e — — — n s 0.22 25t,#26wire,woundona100 1N4997 1N4001 2N6367

or equivalent. Core 5 turnseach.C=1twistedpairof#24wire,8turns. A andB=2twistedpairsof#24wire,8twistsperinch. (Core asabove.) 2 twistedpairsof#20wire,6twistsperinch,4turns (Core asabove.) 2 twistedpairsof#24wire,8twistsperinch,6turns F627-8Q1 orequivalent. B =8turns.Core 2 twistedpairsof#26wire,8twistsperinch,A=4turns — — — c T — a BNCconnectors 0.15 3ferritebeadseach h 2N6368 — l µ i e — s H, moldedchoke 10 .

Stackpole57-9074-11, IndianaGeneralF624-19Q1 c P µ H o µ r H, moldedchoke o m d u c — t Stackpole57-9322-11, IndianaGeneral , RF Application Reports RF Application Ω , 2Wresistor(1.0 µ

H) PRODUCT TRANSFERRED TO M/A–COM

Freescale Semiconductor, Inc... ARCHIVE INFORMATION IMD performancedown can deliver90Watts (PEP)inthe25 at 30MHzbut only13dBat3MHz. actually overcompensated.This stagehasagainof16dB stage, whereefficiency isnotofprimaryconcern, was compensation wasutilizedon thefinalstage.Thedriver by applyingcompensation.For thisreasononly3dBof source andtheinputbalunto thefinalstage. taken witha9:1ratiotransformerconnectedbetween50 compensation onthefinalamplifier stage.Thisdatawas a lowerVSWRovertheband. some degree.This,inturn,shouldresult impedanceto low frequencies,itwillalso equalize theinput at feedback Since thebasisforcompensationistointroducemore error iscausedbyreactiveelementsinthefeedbackpath. frequencieswhere thephaseerrorsaresmall.The low the distortionoriginallygenerated.Thisisonlytrueat is fedbacktotheinputandreamplified,tendingcancel also improvesthelinearity sincesomeoftheoutputsignal it impedance, andreducesthegainof the amplifier. However, to determinethefeedbackslope. frequencies andc)aseriesinductorwithparallelresistor resistor,series tolimittheamountoffeedbackatlow feedback networksconsistof:a)adcblockingcapacitor, b)a the driverandoutputstagesforgaincompensation.The Gain Compensation obtained at6 stage isfrequencycompensated,95Watts (PEP)canbe iue1.Pooo o iwo 25VLna mlfe Figure14.PhotoofBottom12.5VLinearAmplifier Figure 13.PhotoofTop View of12.5VLinearAmplifier RF Application Reports RF Application Without frequencycompensation,thecompletedamplifier From thistableitcanbeseen thatefficiencyreduced is The following two tables illustrate the affect of In general,theuseofnegativefeedbacklowersinput Negative collector-to-basefeedbackisemployedinboth – 10MHz. – 30dB.Ifonlythepower amplifier Freescale Semiconductor,Inc.

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n t f o o : r w m AN593 w Ω a t w i o . f n r e generated across windings b andB are outofphaseand windings generatedacross shown intheFigure.Itcan beseenthatthevoltages windings inthistransformer, anarbitrary3Vinputhasbeen As anexampleofthevoltage relationshipsforthevarious capital lettersrefertothetwo wiresinagiventwisted-pair). the numberofturnsaswinding Aa.(Thelowercaseand with theseriescombinationof aA,lineBbmusthavetwice Examination diagram of transformer T1 isshown inFigure 16. model. The singlecoreapproachwasused in the engineering These winding Aa equal numberofturns(four).Ifasinglecoreisutilized, toroids. Inthetwocoreapproach,bothwindingshavean which canbewoundoneitherasingleortwoseparate O 30 MHz 12 MHz 3 MHz Without Feedback 30 MHz 12 MHz 3 MHz With Feedback Table 2.Performanceof12.5VOutputStageWith and e n A lumped-constantequivalentconventionaltransformer Transformer T1 s c T a h lines mustbewoundbifilaronthecore.SeeFigure15. l i e s . c uses fourturnswhilewindingBbeightturns. P reveals thatsincewindingBisdirectlyinparallel o r 12.5 dB 16.2 dB 19.2 dB 15.3 dB o m Without GainCompensation 12 dB 16 dB GPE GPE d u c consistsoftwotwistedpairswires t , 43.0% 46.8% 48.0% 43.0% 46.5% 45.5% EFF. EFF. – – – – – – 33dB 30dB 26dB 31dB 31dB 30dB IMD IMD VSWR VSWR 1.05 1.05 2.4 6.5 2.1 1.6 7 PRODUCT TRANSFERRED TO M/A–COM

Freescale Semiconductor, Inc... ARCHIVE INFORMATION (3 V cancel eachother. Therefore,theresultingoutputis1V end. SeeFigure15. of eachpairaresoldered togetherateach wires Both core. balun performsthevoltagesubtraction. a 4:1ratiotransformer(aA)and1:1balun(bB),where the 8 Transformer T2 This transformermaybeconsideredasacombinationof – B 2V). Figure 15.Transformer Detailsfor12.5V A Linear Amplifier(seeFigure4) 50 consists oftwotwistedpairsonasingle Pairs Ω Balanced 55.5 T4 C Ω T1 Freescale Semiconductor,Inc.

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n t f o A o : r w m AN593 w a t w i o . f n r e across windingc= across Therefore, theoutputvoltageis3.0voltsand A andbplus1VfromwindingaB). the voltagefrompointDtoEwouldbe3V(1 paralleled points DandEonthediagram.SincewindingsAb are c andCmustequalthevoltagebetween across developed is appliedtotheinput.Itcanbeseenthatvoltage volt T4 andtheratioofvoltagesonvariouswindingsifone allowable withoutnoticeableeffects. to windingcC.Deviationsof 10 possible tothedesiredratioof1:1.5forwindingAaandBb eight turns.Thisisthenearestwhole number of turns unbalanced.BothaAandbButilizefiveturnsCcuses is a singlecore.WindingsaAandbBarebalancedwhileCc soldering thetwowiresateachend. a singlecore.Eachpairistreatedaswireby C12 andC25wereunusuallylargeinvalue. required forthebalun.ForthisreasoncapacitorsC10,C11, is difficultit toobtain thelowcharacteristicimpedance necessary.was compensation Thiswasrequiredbecause the firstversionexceptthatmuchmorehighfrequency very similartothatobtainedfrom were results Performance a balun and anunsymmetrical 1:9ratio transformer. difficult totwistsuch linesuniformly. windings withfourormorepairsshouldbeavoidedasit is O e n Figure 17 shows thelumpedequivalenttransformerof 17 Figure Transformer T4 Transformer T3 A second amplifierwasevaluatedwithT4replacedby A When usingtwisted-pairtransmissionlinetransformers, Figure 16.EquivalentLumpedElementFormofT1 s c T a h

l i e

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and connectedtotheinput,theyseeonevolt.Thus . c P o r o m d u c usesthreeseparatebifilarwindingson alsousestwotwistedpairswound on – t 1.5VandwindingC=V. , RF Application Reports RF Application – 20%ofthisratioare

PRODUCT TRANSFERRED TO M/A–COM

Freescale Semiconductor, Inc... ARCHIVE INFORMATION to meetharmonicsuppressionrequirements.Thisfilter between theamplifieroutputandantennawillberequired Table 2.Thisdatasuggeststhatasuitablelow-pass filter output powerlevelswithasingletonetestareillustratedin given inFigure24. to correlatelowfrequencyreadingsonapowermeterisalso provided inthefollowingcurves.Acalibrationcurveforuse Performance necessity iscommontomostbroadbandamplifierdesigns. necessity

RF Application Reports RF Application The harmonicsuppressionmeasurementstakenatfull Typical performanceofthe12.5voltlinearamplifiersis Figure 17.EquivalentLumpedElementFormofT4 Figure 18.EMDasaFunctionofOutputPowerfor

Push-Pull LinearAmplifier

Freescale Semiconductor,Inc.

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Figure 20.IMDversusFrequency o

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–

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9 PRODUCT TRANSFERRED TO M/A–COM

Freescale Semiconductor, Inc... ARCHIVE INFORMATION a standard2:1 ratiocouplingtransformerinstead ofthe 1:1 performance results.Asimilar amplifierwasconstructedwith impedance match,itiseasytoduplicate forconsistent Although thistypeoftransformerdoes not provide optimum transformers areemployed throughout the12V design. Transformer Data Figure 24.ResponseofH.P. 431 10

As with the 28 V amplifier, transmission line type Figure 22.EfficiencyversusFrequency Figure 23.VSWRversusFrequency Low Frequencies Freescale Semiconductor,Inc.

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n t f o o : r w m AN593 w a t w i o . f n r e impedance duetowire sizesortwistvariations. Although several times larger than the changes in transformer and outputimpedanceovera decadefrequencyrangeare compensation required.Thevariationsinthetransistorinput amplifiers andwillmainlyaffect theamount ofhighfrequency the leastcriticalpointsin designofbroadbandlinear inch willalterthelineimpedance. However, thisisoneof ofdielectric orchangingthenumberoftwistsper thickness at 3MHz. would be250ohms,whichcorrespondsto roughly 14 operatingfrequency. Thismeans thatforT4,thereactance the reactanceofhighimpedanceportatlowest inductance canbedeterminedtohaveatleast4 problem thatoneshouldbefirstconcernedabout. at thehighfrequencies.Excessiveheatingisprimary there wassomeamountofheatgeneratedinthesmalltoroid small enoughnottobenoticedinanoscilloscope.However, toroid ofthesamematerial.The distortionineachcorewas recommended fluxdensity, andthencomparedtoalarger toroids weretestedatthreetofourtimesthemaximum 5 of 1 concern. Forthematerialchoseninthisdesign,alossfactor saturation andheatgeneration. power handlingcapabilitywhichislimitedbybothmagnetic core materials.Thefirstislosses.secondthe such asArco466and469. or bettertolerancefixedvalueunits,variablecapacitors should bewellmatchedandthereforeeither lower IMDathigherfrequencies.CapacitorsC11 andC12 into using transmissionlinetypetransformers. were basicallyunchangedfromtheperformanceofmodel improvement inVSWRatallfrequencieswhilegainandIMD ratio balun (T2). This amplifier featured a 40 a maximumcorelossof1.5 not foundtobeexcessive.Infact,someofthe1/2 100 gausslimitsuggestedfortheparticularcoretype,itwas the 28Vamplifiersection,althoughthisisinexcessof core reducesthedensitytoabout130gauss.Asstatedin wouldberequiredfora1/2 gauss this iswellintothelinearregion. 45 to70gauss.FromtheB-Hcurvesitcanbeseenthat asIndianaGeneral F627-8orStackpole57-9322),is (such maximum recommendedfluxdensityfora1/2 function of flux density and operating frequency. The to lossesismostprevalentathigherfrequencies,beinga firstatlowfrequencies. However,occurs core heating due generated onthecarrierandenvelope.Thissaturation saturation regionofthecorematerial,distortion willbe materials power levelsandremaininthelinearoperatingregionof be aslargepossibletoablehandletherequired consistent withthewiresizeandrequirednumberofturns. the smallestpracticalsizedcoreforinputtransformer While thisfigureseemsnegligible,itisadvantageoustouse O e – n Employing adifferent wiresizeorwithadifferent As aruleofthumb,therequiredminimumtransformer For theinputtransformer(T1)corelossesareofprimary Twoconsidered inthechoiceoftoroidal be must factors Splitting thecompensatingcapacitorfortransformerT2 For the12-voltamplifier, afluxdensityofroughly180 Conversely thecoreofoutputtransformer(T4)should Conversely 10mW/cm s

three parts(C10,C11 andC12)willresultinconsiderably c T – a 2mW/cm h l i e ’ s B-H curve. Ifthecoreisoperatednear B-H . c P o r 3 o m at30MHz.Forthesizeofcore used in T1, d 3 u at3MHzistypical.Thisincreases to c t , – RF Application Reports RF Application 7.0mWcanbe expected. ″ O.D.core.Useofalarger ″ O.D.toroid – 5times – ″ 60% O.D. ± 5% µ H PRODUCT TRANSFERRED TO M/A–COM

Freescale Semiconductor, Inc... ARCHIVE INFORMATION sensitive. Parallelcapacitorsareemployedtoincreasethe their capacitance values are voltage and temperature applications, becausetheyhavespuriousresonancesand, capacitors havebeenavoided,exceptforcertainby-pass collector currents of the 2N6368 transistors. Ceramic the heatsinkfortemperaturecompensationofquiescent in eachendoftheheatsink.DiodeD2ispressfittedinto except thefeed-throughs,areonbacksideofboard (R3, R10),andallby-passcapacitors, resistors bias base which isseparatedfromtheheatsinkby3/32inches.The 0.01 ohmatthelowestenvelopefrequency. must beaslowpossible. impedance levelsinvolved.Thepowersupplyimpedance is extremelyimportantbecauseofthehighcurrentsandlow broadband amplifier, itwaslearnedthatagoodgroundplane mounting screws. From experience with an earlier feedthrough capacitors, the BNC connectors and the are connected together at several points with the given inFigures25and26.Thegroundplanesoneachside two-sided copper-fiberglasslaminate.Afullsizedpatternis Construction Notes(12.5VVersion) envelope. low IMDreadingsdespiteslightflat-toppingofthe fairly is possibletoobtainhigherpowerlevelswith minimizedit higher. impedance ratiosofthetransformerswillbesomewhat impedances usuallybeinghigherthanoptimum,theactual employed. respectively, when4:1and9:1outputtransformersare 28 V and12.5amplifierswouldbe120W50 where amismatchcansignificantlydegradetotallinearity. frequency range,theyaremostseriousintheoutputstage compromises inmatchingarenecessarytotunethewide somewhat criticalcomparedtoahighervoltageunit. level makethelayout,constructionandcomponentselection impedancesinvolvedina12.5volt amplifierofthispower low tors areinsufficient for thesecurrentlevels.Ingeneral, the 1.26A averagecurrents.Eventheleadsizesinmostcapaci- isolation capacitors will have to handle 1.77A peak and Half ofthisissuppliedbyeach2N6368.Thus,thecollector transformer primaryis self resonances. The peakRF current in the output current carryingcapabilityandtodecreasethepossibilityof RF Application Reports RF Application All dc connections aremadeonthebacksideofboard dc All acimpedanceofthesupplyshouldnotbehigherthan The board forbothamplifierdesignsismadeof circuit The Thus, ifthephaseandevenharmonicdistortionsare However,inductances inthecircuit,andline stray to due The maximumtheoreticallinearoutputpowersforthe 6.25 80 W Ω =3.54A. Freescale Semiconductor,Inc.

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n t f o o : r w m AN593 w a t w i o . f n r e CONSTRUCTION NOTES(28VVersion) fixed valuecapacitors. operationoftheunit,theycanbechangedto satisfactory the compensating capacitors. Then after establishing capacitors, suchastheARCO460linebe used initially for It pensation capacitors. is recommended that variable capacitors andthetransformerhighfrequency-com- by-pass the sameprecautionsshouldbetakeningrounding as farthephysicalcircuitlay-outisconcerned.However, O Frequency Harmonic e n The 28voltunitislesscriticalthanthe12.5V amplifier s Table 3.HarmonicSuppressionversusFrequency c T GND IN a h l i e s . Figure 25.BottomPCBoardPattern c P Figure 26.Top SideofPCBoard 30 MHz 12 MHz o r 6 MHz 3 MHz o m d u c t , – – – – 35dB 30dB 17dB 19dB 2nd 6 6 ″ ″ – – – – 25dB 20dB 18dB 15dB 3rd – – – – 50dB 28dB 23dB 26dB 4th OUT V – – – – CC 62dB 34dB 35dB 29dB 5th 11 PRODUCT TRANSFERRED TO M/A–COM

Freescale Semiconductor, Inc... ARCHIVE INFORMATION IMPROVED PERFORMANCE .Hilbers:DesignofH.F. Wideband Power Transformers, 2. Ruthroff: SomeBroadBandTransformers, 1. REFERENCES optimum operation. of these new requiredevices circuit modifications for upgrading the12-Volt amplifierusingthe2N6368.Neither 28-Volt amplifier. The MRF460 isrecommended for substituting theMRF463orMRF464for 2N5942 in the mismatch ruggednesscharacteristicscan be enhanced by improvements have been made. Both IMD and load 12 Philips ApplicationInformation#530. 47 Since theoriginalworkontheseamplifiers,device , August,1957. Freescale Semiconductor,Inc.

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n t f o o : r w m AN593 w a t w i o . f n r e .Granberg, 7. Granberg,H.; 6. Granberg,H.; 5. Pappenfus; Bruene,Schoenike: Single Sideband Prin- 4. .Granberg, 8. Pitzalis-Couse: Broadband Transformer DesignforRF 3. O e n Semiconductor ProductsInc.,September1974. 30 From ThisPush-Pull Amplifier,MHz tor ProductsInc.,June1975. bining Techniques forRF, ciples andCircuits,McGraw-Hill. ucts Inc.,January1975. ucts Linear Amplifiers, conductor ProductsInc.,February1975. 30MHzSSB DriverApplications, to Transistor Amplifiers, s c T a h l i e s . c P o r H.; H.; o m d A ComplementarySymmetryAmplifierfor2 A Measuring theIntermodulationDistortion of Broadband Transformers andPowerCom- u Get 300Watts PEPLinearAcross2to c t EB-38 MotorolaSemiconductorProd- , ECOM-2989, AN-749 MotorolaSemiconduc- RF Application Reports RF Application EB-32 MotorolaSemi- July 1968. EB-27 Motorola

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Freescale Semiconductor, Inc... ARCHIVE INFORMATION ◊ ASIA PACIFIC: MotorolaSemiconductorsH.K.Ltd.;SiliconHarbourCenter, No.2DaiKing Street,Tai PoIndustrialEstate,Tai P JAPAN: NipponMotorolaLtd.;4-32-1, Nishi-Gotanda,Shinagawa-ku,Tokyo 141, Japan. EUROPE: MotorolaLtd.;EuropeanLiterature Centre;88Tanners Drive,Blakelands,MiltonKeynes,MK145BP, England. USA: MotorolaLiteratureDistribution; P.O. Box20912;Phoenix,Arizona85036. Literature DistributionCenters: RF Application Reports RF Application oooaad areregisteredtrademarks ofMotorola,Inc.isanEqualOpportunity/Affirmative ActionEmployer. Motorola and associated withsuch unintendedorunauthorizeduse,evenifsuchclaimallegesthatMotorolawasnegligentregardingthedesig against allclaims,costs,damages,andexpenses,reasonableattorneyfeesarisingoutof,directlyorindirectly, anyclai unintended orunauthorizedapplication,BuyershallindemnifyandholdMotorola occur.themay death or Motorolaproductcouldcreateasituationwherepersonalinjury ShouldBuyerpurchaseoruseMotorola systems intendedforsurgicalimplantintothebody, orotherapplicationsintendedtosupportsustainlife,foranyothe not conveyanylicenseunderitspatentrightsnortheofothers.Motorola productsarenotdesigned,intended,orauth applications. Alloperatingparameters,including specificallydisclaimsanyandallliability,and includingwithoutlimitationconsequentialorincidentaldamages. the suitabilityofitsproductsforanyparticularpurpose,nordoesMotorolaassumeliability arisingoutoftheapplicati Motorola reserves therighttomakechangeswithoutfurthernoticeanyproductsherein. Motorolamakesnowarranty, representationo Freescale Semiconductor,Inc.

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c P o r o m d u c “ Typical t , ” parameterscananddovaryindif ’ s technicalexperts.Motoroladoes on oruseofanyproductcircuit, r applicationinwhichthefailureof orized foruseascomponentsin o, N.T., HongKong. m ofpersonalinjuryordeath n ormanufactureofthepart. products foranysuch r guaranteeregarding AN593/D ferent 13 PRODUCT TRANSFERRED TO M/A–COM