2018《電路分析與電子線路》綜合訓(xùn)練題

1、2018年電路分析與電子線路綜合訓(xùn)練題注意：2018年電路分析與電子線路綜合訓(xùn)練組隊共同討論完成綜合訓(xùn)練題目3-4題，以書面形式撰寫報告，需要詳細的討論過程和仿真的結(jié)果。請同學(xué)們自學(xué)“數(shù)值分析軟件(如MATLAB等)及電路仿真軟件(如Multisim或Pspice等)”。提交書面報告時間：6月20日前。Project1PowerSuppliesObjective:Thisprojectwillshowsomeofthebasicprinciplesofpowersuppliesusingfullwaverectifier,Zenerdiode,andfixed-voltageregulator

2、circuits.Components:BridgeRectifier(50PIV,1A),Zenerdiode(10Vat500mW),7805regulatorIntroduction:Mostofthedirectcurrent(DC)powerusedinelectronicdevicesisderivedbyconverting60Hz,115Valternatingcurrent(AC)powertodirectcurrentpower.ThisACtoDCconversionusuallyinvolvesastep-downtransformer,rectifier,filter

3、,andaregulator.Thestep-downtransformerisusedtodecreasetheAClinevoltagefrom115RVMStoanRMSvalueneartheDCvoltageneeded.Theoutputofthestep-downtransformeristhenfedintoadioderectifiercircuitthatonlyoutputspositivehalvesoftheinputsinusoid.Afilteristhenusedtosmooththerectifieroutputtoachieveanearlyconstant

4、DCvoltagelevel.Aregulatorcanbeaddedafterthefiltertoensureaconstantoutputvoltageinspiteofchangesinloadcurrentandinputvoltages.Twodifferenttypesofvoltageregulatorswillbeusedinthisproject.ThefirstinvolvesaZenerdiodecircuitandthesecondinvolvesavoltageregulatorcircuit.AZenerdiodecanbeusedasavoltageregula

5、torwhenthediodeisreversebiasedandoperatedinthebreakdownregion.Tomaintainvoltageregulation,theZenerdiodemustbeoperatedinthebreakdownregionatacurrentgreaterthanthekneecurrentZ(KI).ForcurrentsgreaterthanIZK,theZenerdiodecharacteristiccurveisnearlyverticalandthevoltageacrossthediodechangesverylittle.Ofc

6、oursethereisamaximumcurrentthediodecantolerate,sogoodregulationisprovidedwhenthediodeisreversebiasedwithcurrentsbetweenZIKandIZMAX.Zenerdiodesareavailablewithawidevarietyofbreakdownvoltages.Anothertypeofvoltageregulatorisavailablewiththe7800seriesregulators.Thisseriesoffixed-voltageregulatorsisnumbe

7、red78xx,wherexxcorrespondstothevalueoftheoutputvoltage.Outputvoltagesfrom5to24voltsareavailable.Theseregulatorsareeasytouseandworkverywell.Design:FindapproximationsfortheDCvoltagelevelandACpeaktopeakripplevoltageforthebridgerectifierandfiltercircuitofFigure1-1.FortheZenerdioderegulatorcircuitofFigur

8、e1-2assumethattheZenerdiodewillregulateat10Voveracurrentrangeof5mAto25mA.AssumingthatthecurrentflowingthroughRisalwaysbetween5mAand25mAandtheZenerdiodeisregulatingat10V,findtheminimumvaluesofRandRLrequired.Youmayassumetheforwarddiodedropforthetwodiodesis1V.LabProcedure:Constructthebridgerectifiercir

9、cuitofFigure1-1withoutthecapacitor.UsetheVariacwiththestep-downtransformerfortheinputvoltagetothebridgerectifier.WiththetransformerpluggedintotheVariac,adjusttheVariacuntilthesecondaryvoltagefromthetransformerequals12VRMS.BECAREFULnottoshortthesecondaryterminals!Observethesecondarywaveformontheoscil

10、loscope.PuttheoscilloscopeonDCcouplingandobservetheloadvoltagewaveformVL.Rememberthatboththeinputsourceandtheloadcannotshareacommongroundterminal.Removepowerfromthecircuit.InsertthecapacitorasshowninFigure1-1beingsuretoobservethecorrectpolarity.Energizethecircuit.WiththeoscilloscopeonDCcouplingobser

11、veVL.MeasuretheDCvoltagelevelusingthedigitalvoltmeter.WiththeoscilloscopeonACcouplingobservetheripplevoltageVR.Comparethesemeasuredvalueswiththecalculatedvalues.Observetheeffectofloadingonthecircuitbychangingtheloadresistorfrom1kQto500Q.MeasuretheDCvoltagelevelwiththedigitalvoltmeter.Observetherippl

12、evoltagewiththeoscilloscopesetonACcoupling.Comparethesevalueswiththepreviouslyrecordedvalues.RecordtheZenerdiodecharacteristiccurvefromthedigitalcurvetracer.Notethevalueofthebreakdownvoltageinthebreakdownregion.AlsonotethevalueofthekneecurrentIZK.AfterverifyingyourdesignedvaluesforRandRLwiththeinstr

13、uctor,constructtheZenerdioderegulatorcircuitofFigure1-2.MeasuretheDCvoltagelevelwiththedigitalvoltmeterfortheminimumvalueofLRalongwithseveralvaluesaboveandbelowtheminimumvalue.BecarefulnottooverloadtheZenerdiode.Commentonthecircuitsoperationforthesedifferentloadresistances.Constructthe7805regulatorc

14、ircuitofFigure1-3beingcarefultoobservethecorrectpinconfigurationoftheregulator.MeasuretheloadvoltageforRLequalto300Q,200Q,and100Q.Calculatethecurrentforeachofthesecases.Doesthevalueoftheloadresistoraffecttheoutputvoltage?UsingRLequalto200Q,recordthe7805regulatorinputvoltage(pin1)andoutputvoltage(pin

15、3).DecreasetheregulatorinputvoltagebydecreasingthesettingoftheVariac.Foreachdecreaseinamplitude,recordtheregulatorinputandoutputvoltages.Continuedecreasingtheamplitudeuntiltheoutputoftheregulatordropsameasurableamountbelow5V.Whatistheminimuminputvoltageneededforthe7805regulatortoproducea5Voutput?Que

16、stions:Whycanttheinputsourceandloadhaveacommongroundinthebridgerectifiercircuit?CantheZenerdiodebeusedasaconventionaldiode?Explainyouranswerandverifywithacurvefromthecurvetracer.Wouldthevalueoftheoutputfiltercapacitorhavetoincrease,decrease,orremainthesametomaintainthesameripplevoltageifthebridgerec

17、tifierwerechangedtoahalf-waverectifier?Explainyouranswer.Howwouldincreasingthefrequencyoftheinputsourceaffecttheripplevoltageassumingallcomponentsremainedthesame?Project2AnalogApplicationsoftheOperationalAmplifierObjective:Thisprojectwilldemonstratesomeoftheanalogapplicationsofanoperationalamplifier

18、throughasummingcircuitandabandpassfiltercircuit.Components:741op-ampIntroduction:Figure2-1showsaweightedsummercircuitintheinvertingconfiguration.Thiscircuitcanbeusedtosumindividualinputsignalswithavariablegainforeachsignal.Thevirtualgroundattheinvertinginputterminaloftheop-ampkeepstheinputsignalsiso

19、latedfromeachother.Thisisolationmakesitpossibleforeachinputtobesummedwithadifferentgain.ThebandpassfiltershowninFigure2-2usesanop-ampincombinationwithresistorsandcapacitors.Sincetheop-ampcanincreasethegainofthefilter,thefilterisclassifiedasanactivefilter.Thisbandpassfiltercircuitisextremelyusefulbec

20、ausethecenterfrequencycanbechangedbyvaryingaresistorinsteadofchangingthevaluesofthecapacitors.Thecenterfrequencyisgivenby:ThecenterfrequencycanbechangedbyvaryingthevariableresistorR3.IncreasingR3decreasesthecenterfrequencywhiledecreasingR3increasesthecenterfrequency.Thebandwidthisgivenby:Noticethatt

21、hebandwidthisindependentofthevariableresistor3Rsothecenterfrequencymaybevariedwithoutchangingthevalueofthebandwidth.Thegainatthecenterfrequencyofthebandpassfilterisgivenby:Design:1.FindtherelationshipsummercircuitofFigurebetweentheoutputandinputsfortheweighted2-1.Designabandpassfilterwithacenterfreq

22、uencyof2.0kHzandabandwidthof200Hz.Letthevoltagegainatthecenterfrequencybe20.CheckyourdesignwithPSPICE.Use15Vsuppliesfortheo-pamp.UseRl=2.4kQ.Figure2-1:WeightedSummerFigure2-2:BandpassFilterLabProcedure:ConstructthesummingamplifierofFigure2-1.DesignforthetransferfunctiontobeVO=-2VIN1-VIN2.Use15Vsuppl

23、iesfortheop-amp.UseRL=2.4kQ.LetVIN1bea1Vpeaksinewaveat1kHzandVIN2equalto5VDC.Verifytheamplifiersoperationbymonitoringtheoutputwaveformontheoscilloscope.ConstructthebandpassfilterofFigure2-2.Usethedesignedvaluesfortheresistorsandcapacitors.Use15Vsuppliesfortheop-amp.UseRL=2.4k.Recordandplotthefrequen

24、cyresponse(youmaywanttousecomputercontrolforthesweepanddatacollection).Findthecenterfrequency,cornerfrequencies,bandwidth,andcenterfrequencyvoltagegaintoverifythatthespecificationshavebeenmet.ChangeR3tolowerthecenterfrequencyfrom2.0kHzto1.0kHz.Repeatpart4forthenewfrequencyresponse.Verifythatthenewce

25、nterfrequencyis1.0kHz.Whatisthenewbandwidth?Whatisthenewcenterfrequencyvoltagegain?ComparewiththemeasurementsofProcedure4.Questions:1.Couldthesummercircuitbeusedwiththeinputsconnectedtothenoninvertingterminalandproducethesameaffectwithouttheinversion?Explain.2.Whatis/arethebenefit(s)ofusinganop-ampc

26、ircuittoproduceabandpassfilteroverusinganRLCcircuitwithanoninvertingop-ampattheoutputoftheRLCcircuit?Project3AnalogComputerApplicationsusingtheOperationalAmplifierObjective:Thisprojectwillfocusontheuseoftheoperationalamplifierinperformingthemathematicaloperationsofintegrationanddifferentiation.Thede

27、signofasimplecircuit(analogcomputer)tosolveadifferentialequationwillalsobeincluded.Components:741op-ampIntroduction:Figures3-1and3-2illustratetwoop-ampbasedcircuitsdesignedtoperformdifferentiationandintegrationrespectively.Theoperationsareperformedreal-timeandcanbehelpfulinobservingbothinitialtransi

28、entsandsteadystateresponse.Theanalysisofthecircuitsisbasedontheidealop-ampassumptionsandperformedinthetimedomain.TheresistorRIshowninthetwocircuitsisincludedtohelpwithstabilityandforgeneralcircuitprotection.ThevalueforRIisnominallysetequaltothefeedbackresistor(Figure3-1)ortheinputresistor(Figure3-2)

29、.Thepurposeoftheoptionalresistorisleftforstudentinvestigationinconjunctionwiththesummaryquestions.Thedifferentiatorandintegratorcircuitsmaybecombinedwithstandardinvertingandnon-invertingop-ampcircuitstoprovidethebuildingblocksforanalogcomputers.Theresultantanalogcomputercircuitsaredesignedtosolvedif

30、ferentialand/orintegral/differentialequationsinarealtimeenvironment.Theabilitytoeasilyinclude,andchange,initialconditionsandforcingfunctionsareadditionalbenefitsoftheanalogcomputers.Figure3-3illustratesacircuitdesignedtosolvethesecondorderdifferentialequationKY-Y=0withtheinitialconditionY(0)=-VXandK

31、=R1R2C1C2.Theinitialconditionissetbyusingthemomentarycontactswitchtoforcetheoutputtoequaltheappliedvoltageatt=0(thetimetheswitchisclosed).Whilethemajoradvancesindigitalcomputersanddigitalsignalprocessinghavereducedtheuseofthesethreecircuits,theyarestillafastandrelativelyinexpensivemethodforprocessco

32、ntrolandstability/operationanalysisforsystemsthatcanberepresentedintermsofdifferentialequations.Design:1.DerivetheexpressionsrelatingtheinputandoutputsignalsforthecircuitsshowninFigures3-1and3-2.12-0.5=/2.Designananalogcomputertosolve必砒withy(0)=2.Solvethedifferentialequationwhenf(t)=0andverifyyourre

33、sultsusingPSpice.Figure3-1:DifferentiatorFigure3-2:IntegratorFigure3-3:AnalogComputer(linear,secondorder,homogenousdifferentialequation)LabProcedure:1.ConstructthecircuitshowninFigure3-1.Use15Vsuppliesfortheop-ampandaloadresistanceof沁2.4kQ.2.Verifytheoperationofthecircuitusinga500mVpeak,50Hzsinewave

34、astheinputsignal.Besuretodesignthegainsuchthattheoutputdoesnotsaturate.Repeatstep2withasinewavefrequencyof500Hz.Doesthecircuitstilloperatecorrectly?Whatchangesneedtobemadetopreventoutputsaturation?Repeatsteps2and3usingatrianglewaveandthenusingasquarewavewiththesamemagnitudesandfrequenciesasusedinste

35、ps2and3.ConstructthecircuitshowninFigure3-2.Again,use15Vsuppliesfortheop-ampandaloadresistanceof2.4kQ.Repeatsteps2through4forthiscircuit.Besuretoadjustyourgainasnecessarytomaintainanoutputsignalwithinthesaturationlimitsof沁土12V.Constructthecircuitdesignedtosolvethedifferentialequationinpart2ofthedesi

36、gnsection.Verifytheoperationofthedesignusingthreedifferentinputwaves(sine,triangle,andsquare).Determinetheoperationforatleastthreedifferentfrequencies-10Hz,1kHz,and100kHz.Explainanydifferencesinoperationofthecircuit.Whataffectdoestheinitialconditionhaveontheresult?Questions:Howcouldyouusethedifferen

37、tiatortoobtainanestimateoftheslewratefortheop-amp?Whyshouldyouincludearesistorinparallelwiththecapacitorintheintegrator?Whatisthepurposeoftheresistorinserieswiththeinputcapacitorinthedifferentiator?Isitpossibletodesignacircuittoperformthedifferentiationandintegrationfunctionsusingthenon-invertinginp

38、ut?Explainyouranswer.Project4CommonEmitterAmplifier(designedfortwolabperiods)Objective:Thisprojectwillshowhowtheh-parametersforaBJTcanbemeasuredandusedinanequivalentcircuitmodelfortheBJT.ACEsmallsignalamplifierwillbebiasedanddesignedtospecificationsalongwithbothlowandhighfrequencyresponseandadjustme

39、nt.Series-seriesfeedbackwillalsobeusedtocontrolthebandwidthandinputimpedanceoftheCEamplifier.Components:2N2222BJTIntroduction:Inorderforcircuitsinvolvingtransistorstobeanalyzed,theterminalbehaviorofthetransistormustbecharacterizedbyamodel.TwoofthemodelsoftenusedforaBJTarethehybridandtheh-parametermo

40、dels.Thecompletehybrid-兀circuitmodelfortheBJTisshowninFigure9-1.ThismodelincludestheinternalcapacitancesandoutputresistanceoftheBJT.Inclusionoftheinternaltransistorcapacitancesmakesthehybrid兀modelvalidthroughouttheentirefrequencyrangeofthetransistor.TypicaldatasheetvaluesofC冗andare13pFand8pFrespecti

41、vely.ThesevaluesaresosmallthatandQmaybeconsideredopencircuitsformidbandfrequencies.Theresistancerxtypicallyhasavalueinthetensofohmsandcanbeconsideredashortcircuitwhilerandroareusuallyextremelylargeinvalueandcanbeconsideredopencircuits.Theh-parametersmallsignalmodelfortheBJTischaracterizedbythefourhp

42、arametersandisshowninFigure92.Unlikethehybrid兀model,theh-parametermodeldoesnotordinarilyincludefrequencyrelatedeffectsandcomponentsandisthereforegenerallyvalidonlyatmidbandfrequenciesandbelow.HoweverthehparametermodelisveryusefulsincethehparameterscanbeeasilymeasuredforaBJT.Thevalueofhreisusuallyont

43、heorderof104andcanbeconsideredashortcircuit.Thevalueofhoeisusuallyontheorderof105Smaking1/hoeeffectivelyanopencircuitformostcircuitconfigurationsandbiases.Makingthesameassumptions,thehybridiandhparametermodelsareequivalentatmidbandfrequencies.Foratransistortooperateasanamplifier,itmusthaveastablebia

44、sintheactiveregion.Tobiasatransistor,aconstantDCcurrentmustbeestablishedinthecollectorandemitter.Thiscurrentshouldbeasinsensitiveaspossibletovariationsintemperatureandp(orhfe).Thevoltageacrossthebase-emitterjunctiondecreasesabout2mVforeach1Criseintemperature,thereforeitisimportanttostabilizeBEVtoens

45、urethatthetransistordoesnotoverheat.ThecircuitshowninFigure9-3isthebiasingschememostoftenusedfordiscretetransistorcircuits.Forthiscircuit,thebaseissuppliedwithafractionofthesupplyvoltageVCCthroughthevoltagedividerRB1,RB2.Foreaseofcircuitanalysis,theTheveninequivalentcircuitshowninFigure9-4canreplace

46、thevoltagedividernetwork.ToensurethattheemittercurrentisinsensitivetovariationsinpandVbe,VbbshouldbemuchgreaterthanVbeandRbbshouldbemuchlessthanPRe.Rbbisusually20-30%oftheproductpRE.ThevoltageacrossREisalsousually2-3voltsforgoodpstabilization.ThissamebiasingschemecanbeusedforallthreeoftheBJTamplifie

47、rconfigurations(CB,CC,CE).TheBJTCEamplifierisshowninFigure9-5.Thesignalsourceandresistiveloadarecapacitivelycoupledtotheamplifier.ThecouplingcapacitorsC1andC2,emitterbypasscapacitorCE,andinternaltransistorcapacitancesshapethefrequencyresponseoftheamplifier.Atypicalamplifierfrequencyresponsecurveissh

48、owninFigure9-6.ThelowhalfpowercornerfrequencyFLiscontrolledbytheinputandoutputcouplingcapacitorsandtheemitterbypasscapacitor.ThehighhalfpowercornerfrequencyFHiscontrolledbytheinternaltransistorcapacitancesandanyseparateloadcapacitor.Thebandwidthisthedifferencebetweenthehighandlowcornerfrequencies(HF

49、-FL).Asthesignalfrequencydropsbelowmidband,theimpedanceofthecouplingcapacitorsC1andC2andemitterbypasscapacitorCEincreases.Thecouplingcapacitorsdropmoresignalvoltageandtheemitterbypasscapacitorbeginstoopenupandcausesincreasedseries-seriesfeedbackresultinginareductionofthegain.OnemethodofrelatingC1,C2

50、,andCEtothelowcutofffrequencyistheshortcircuittimeconstantmethod.Thetimeconstantmethodisadvantageousbecauseitprovidesanapproximatevalueforthecutofffrequencieswithoutexactlyfindingallthepolesandzerosofacircuit.Thetimeconstantmethodalsohelpsshowwhichcapacitorsaredominantindeterminingthecornerfrequenci

51、es.TheshortcircuittimeconstantmethodrelatesFLandcircuitcapacitorsby:whereFListhelowhalfpowerfrequency,ncisthenumberofcouplingandbypasscapacitorsinthecircuit,andiCisthevalue,inFarads,oftheithcapacitor.Risistheresistancefacingtheithcapacitorwiththeithcapacitorremovedandallothercouplingandbypasscapacit

52、orsreplacedbyshortcircuitsandtheinputsignalreducedtozero.Thisresistancecalculationisrepeatedforeachcouplingandbypasscapacitorinthecircuit.Theinternalcapacitancesofatransistorhavevaluesinthepicofarad(pF)rangethatbegintodecreasethegainoftheamplifierforfrequenciesabovemidband.Amethodofrelatingtheintern

53、altransistorcapacitancesCKandGtothehighcutofffrequencyistheopencircuittimeconstantmethod.ThismethodrelatesFHandtheinternaltransistorcapacitancesby:whereFHisthehighhalfpowerfrequency,ncisthenumberofinternaltransistorcapacitorsinthecircuit,andiCisthevalue,inFarads,oftheithcapacitor.Rioistheresistancef

54、acingtheithcapacitorwiththeithcapacitorremovedandallinternaltransistorcapacitorsreplacedbyopencircuitsandtheinputsignalreducedtozero.Thisresistancecalculationisrepeatedforeachinternaltransistorcapacitorinthecircuit.WhentheemitterresistoroftheCEamplifierisleftunbypassed,theinputcurrentsignalflowsthro

55、ughtheunbypassedemitterresistorasdoestheoutputsignalcurrent.ThisunbypassedemitterresistorintheCEamplifierproducesseries-seriesfeedback.ThefeedbackresistorisER.Feedbackisusedinamplifierstocontrolinputandoutputimpedances,extendbandwidth,enhancesignal-to-noiseratio,andreduceparametersensitivity.Thesefe

56、edbackperformanceimprovementsareallattheexpenseofgainintheamplifier.Figure4一1:Hybrid-兀BJTModelFigure4-2:hParameterBJTModelFigure4-3:BJTTypicalBiasingCircuitFigure4-4:TheveninEquivalentBiasingCircuitFigure4-5:CommonEmitterAmplifierFigure4-6:TypicalAmplifierFrequencyBodeDiagramDesign:Designacommonemit

57、teramplifierwithRERE1+RE2completelybypassedwiththefollowingspecifications:usea2N2222BJTanda12voltDCsupplymidbandgainVo/Vs50lowcutofffrequencyFLbetween100Hzand200Hzinputimpedanceasseenbythesource1kQVosymmetricswing2.0voltspeak(4Vp-p)loadresistorRL=1.5kQsourceresistanceRs=50Q(thisisinadditiontothefunc

58、tiongeneratorsinternalresistance)LabProcedure:(steps1and2maybeomittedifdonepriortothislabperiodandthesameBJTisused)Fromthedigitalcurvetracer,findthevalueofBdcandPacatthedesignedQ-pointoftheCEamplifier.RememberPdc二Ic/IbandPac二AIc/AIb-HowdothetwoPvaluescompare?Determinethevaluesofhoeandhiefromthedigit

59、alcurvetracer.TheslopeofthetransistorIc-VcEcurvesintheactiveregionishoe.Findhiebylookingatthebase-emitterjunctionasadiodeonthecurvetracer.ThetangentslopeoftheIB-VBEcurveattheIBQpointis1/hie.constructthecEamplifierofFigure9-5.RemembersRisinstalledinadditiontotheinternal50Qresistanceofthefunctiongener

60、ator.Notethat(Rei+Re2)shouldequalthedesignedvalueforReandRei沁Re2-VerifythatthespecificationshavebeenmetbymeasuringtheQ-point,midbandvoltagegain,andpeaksymmetricoutputvoltageswing.Noteanydistortionintheoutputsignal.ObservetheloadingaffectbyreplacingRLfirstby150Qandthenby15kQ.Noteanychangesintheoutput