微电子电路microelectroniccircuit标准课件sedra著作

1OutputStagesandPowerAmplifiersMicroelectronicCircuits-FifthEditionSedra/Smith2Copyright2004byOxfordUniversityPress,Inc.Figure14.1Collectorcurrentwaveformsfortransistorsoperatingin(a)classA,(b)classB,MicroelectronicCircuits-FifthEditionSedra/Smith3Copyright2004byOxfordUniversityPress,Inc.Figure14.1(Continued)(c)classAB,and(d)classCamplifierstages.MicroelectronicCircuits-FifthEditionSedra/Smith4Copyright2004byOxfordUniversityPress,Inc.Figure14.2Anemitterfollower(Q1)biasedwithaconstantcurrentIsuppliedbytransistorQ2.MicroelectronicCircuits-FifthEditionSedra/Smith5Copyright2004byOxfordUniversityPress,Inc.Figure14.3TransfercharacteristicoftheemitterfollowerinFig.14.2.ThislinearcharacteristicisobtainedbyneglectingthechangeinvBE1withiL.ThemaximumpositiveoutputisdeterminedbythesaturationofQ1.Inthenegativedirection,thelimitofthelinearregionisdeterminedeitherbyQ1turningofforbyQ2saturating,dependingonthevaluesofIandRL.MicroelectronicCircuits-FifthEditionSedra/Smith6Copyright2004byOxfordUniversityPress,Inc.Figure14.4MaximumsignalwaveformsintheclassAoutputstageofFig.14.2undertheconditionI=VCC/RLor,equivalently,RL=VCC/I.MicroelectronicCircuits-FifthEditionSedra/Smith7Copyright2004byOxfordUniversityPress,Inc.Figure14.5AclassBoutputstage.MicroelectronicCircuits-FifthEditionSedra/Smith8Copyright2004byOxfordUniversityPress,Inc.Figure14.6TransfercharacteristicfortheclassBoutputstageinFig.14.5.MicroelectronicCircuits-FifthEditionSedra/Smith9Copyright2004byOxfordUniversityPress,Inc.Figure14.7IllustratinghowthedeadbandintheclassBtransfercharacteristicresultsincrossoverdistortion.MicroelectronicCircuits-FifthEditionSedra/Smith10Copyright2004byOxfordUniversityPress,Inc.Figure14.8PowerdissipationoftheclassBoutputstageversusamplitudeoftheoutputsinusoid.MicroelectronicCircuits-FifthEditionSedra/Smith11Copyright2004byOxfordUniversityPress,Inc.Figure14.9ClassBcircuitwithanopampconnectedinanegative-feedbacklooptoreducecrossoverdistortion.MicroelectronicCircuits-FifthEditionSedra/Smith12Copyright2004byOxfordUniversityPress,Inc.Figure14.10ClassBoutputstageoperatedwithasinglepowersupply.MicroelectronicCircuits-FifthEditionSedra/Smith13Copyright2004byOxfordUniversityPress,Inc.Figure14.11ClassABoutputstage.AbiasvoltageVBBisappliedbetweenthebasesofQNandQP,givingrisetoabiascurrentIQgivenbyEq.(14.23).Thus,forsmallvI,bothtransistorsconductandcrossoverdistortionisalmostcompletelyeliminated.MicroelectronicCircuits-FifthEditionSedra/Smith14Copyright2004byOxfordUniversityPress,Inc.Figure14.12TransfercharacteristicoftheclassABstageinFig.14.11.MicroelectronicCircuits-FifthEditionSedra/Smith15Copyright2004byOxfordUniversityPress,Inc.Figure14.13Determiningthesmall-signaloutputresistanceoftheclassABcircuitofFig.14.11.MicroelectronicCircuits-FifthEditionSedra/Smith16Copyright2004byOxfordUniversityPress,Inc.Figure14.14AclassABoutputstageutilizingdiodesforbiasing.Ifthejunctionareaoftheoutputdevices,QNandQP,isntimesthatofthebiasingdevicesD1andD2,andaquiescentcurrentIQ=nIBIASflowsintheoutputdevices.MicroelectronicCircuits-FifthEditionSedra/Smith17Copyright2004byOxfordUniversityPress,Inc.Figure14.15AclassABoutputstageutilizingaVBEmultiplierforbiasing.MicroelectronicCircuits-FifthEditionSedra/Smith18Copyright2004byOxfordUniversityPress,Inc.Figure14.16Adiscrete-circuitclassABoutputstagewithapotentiometerusedintheVBEmultiplier.ThepotentiometerisadjustedtoyieldthedesiredvalueofquiescentcurrentinQNandQP.MicroelectronicCircuits-FifthEditionSedra/Smith19Copyright2004byOxfordUniversityPress,Inc.Figure14.17Electricalequivalentcircuitofthethermal-conductionprocess;TJ–TA=PDqJA.MicroelectronicCircuits-FifthEditionSedra/Smith20Copyright2004byOxfordUniversityPress,Inc.Figure14.18MaximumallowablepowerdissipationversusambienttemperatureforaBJToperatedinfreeair.Thisisknownasa“power-derating”curve.MicroelectronicCircuits-FifthEditionSedra/Smith21Copyright2004byOxfordUniversityPress,Inc.Figure14.19ThepopularTO3packageforpowertransistors.Thecaseismetalwithadiameterofabout2.2cm;theoutsidedimensionofthe“seatingplane”isabout4cm.Theseatingplanehastwoholesforscrewstoboltittoaheatsink.Thecollectoriselectricallyconnectedtothecase.Thereforeanelectricallyinsulatingbutthermallyconductingspacerisusedbetweenthetransistorcaseandthe“heatsink.”MicroelectronicCircuits-FifthEditionSedra/Smith22Copyright2004byOxfordUniversityPress,Inc.Figure14.20Electricalanalogofthethermalconductionprocesswhenaheatsinkisutilized.MicroelectronicCircuits-FifthEditionSedra/Smith23Copyright2004byOxfordUniversityPress,Inc.Figure14.21Maximumallowablepowerdissipationversustransistor-casetemperature.MicroelectronicCircuits-FifthEditionSedra/Smith24Copyright2004byOxfordUniversityPress,Inc.Figure14.22ThermalequivalentcircuitforExample14.5.MicroelectronicCircuits-FifthEditionSedra/Smith25Copyright2004byOxfordUniversityPress,Inc.Figure14.23Safeoperatingarea(SOA)ofaBJT.MicroelectronicCircuits-FifthEditionSedra/Smith26Copyright2004byOxfordUniversityPress,Inc.Figure14.24AclassABoutputstagewithaninputbuf