pspice PSpice_ch12

PSPICE计算机仿真 SimulationProgramwithIntegratedCircuitEmphasis CH12 FREQUENCYRESPONSE频率响应 12 1specifyingfrequencyvariationandnumber SinusoidalLinear LogarithmicDecade octave 12 2frequencyresponseoutput Rectangular polar decibel Example18illustrateshowtoanalyzethefrequencyresponseofaparallelRLCcircuitwithPSpice Fig 104ddb Example18 a ThecurrentsourceinthecircuitshowninFig 104is50cos tmA UseProbetoplotVoversusffrom1000to2000Hzinincrementsof10Hzonalinearfrequencyscale b FromtheProbeplot estimatetheresonantfrequency thebandwidth andthequalityfactorofthecircuit c Comparetheresultsobtainedinb withananalyticsolutionforf0 andQ Solutiona b Fig 105sch Fig 106setting UsingtheProbeCursor wenotethatthepeakamplitude 峰值振幅 ofabout400Voccursatafrequencyof1590HzinFig 107a Thusweestimatetheresonantfrequency 衰减频率 at1590Hz Fig 107aprobe Toestimatethebandwidth weusebothcursorstofindthefrequencieswhereVo 399 697 1 414 282 67V Theclosestvaluesare281 992at1552Hzand1632 1Hz Fig 107b Thusweestimatethebandwidthtobe1632 1 1552 orabout80Hz Fig 107b Wecalculatethequalityfactorfromtherelationship Solutionc Adirectanalysisofthecircuityields Comparison Example19 Example19 ModifythePSpiceschematicforExample18tostepthecapacitorvaluesfrom0 15 Fthrough0 35 F ThenuseProbetodisplaythefrequencyresponsecharacteristicsforallvaluesofcapacitance Commentontheeffectofthechangingcapacitance Solution Fig 108sch Fig 108aparamproperty Fig 108bsetting Fig 108cParam setting Fig 109Probe Result Thesmallestvalueofcapacitanceproducedtheplotfarthesttotheright WeexpectthisresultbecausetheequationforresonantfrequencyforanRLCcircuitis Furthermore asthecapacitanceincreases theresonantpeakbecomessharper Thisresult too comesasnosurprisebecausetheequationforQinaparallelRLCcircuitis 12 3Bodeplotswithprobe Fig 110ddb Example20comparestheexactdBvoltagemagnitudeversuslogfrequencyandphaseangleversuslogfrequencyplotstotheBodestraight lineapproximationusingProbe Example20 ConstructaPSpiceschematicandassociatedanalysistogeneratethefrequencyresponseofthecircuitshowninFig 110forthreedifferentvaluesofresistance 5 50 and500 ThenuseProbetoplottheoutputvoltagemagnitudeindBandoutputvoltagephaseangleversuslogfrequency Finally usetheLabeltoolinProbetooverlayastraight lineBodeapproximationplotandcomment Fig 111sch BecausethisisaseriesRLCcircuit weknowthatthecentrefrequencyandthebandwidtharegivenby ForthecircuitshowninFig 110 thecentrefrequencyis Thebandwidthranges Fig 111aparam property Fig 111bvac property Fig 111csetting1 Fig 111dsetting2 Fig 112aPlot Addplottowindow 选中上面窗口 SEL 表示选中 Trace Addtrace先选择右侧DB 再选择左侧V out 底部出现 DB V out Fig 112bselectDB V out 选中下面窗口 SEL 表示选中 Trace Addtrace先选择右侧P 再选择左侧V out 底部出现 P V out Fig 112cselectP V out Fig 112probe 12 4Filterdesign Example21demonstratestheuseofPSpiceandProbeinverifyingthebehaviorofahigh Qbandpassfilter Fig 113ddb Example21 ThecircuitinFig 113isanactivehigh Qbandpassfilter Using1nFcapacitorsandanidealopamp designvaluesforthethreeresistorstoyieldacentrefrequencyof10KHz aqualityfactorof10 andapassbandgainof3 UseProbetoverifythattheresistorvaluesyoucomputeproduceafilterthatsatisf