电子专业参赛课件 数字电子技术(课件)lec25

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1、2021/8/22Chapter7Latches,Flip-Flops,andTimers1Lecture25MainContentsLecture25SchmittTrigger,One-shotsSchmitttriggerworkingprincipleandapplication;Twotypesofone-shot:differentiation/integration;Integratedone-shotapplication.2021/8/22Chapter7Latches,Flip-Flops,andTimers2CMO

2、SSchmittTrigger(常用的脉冲整形电路)Lecture25SchmittTrigger,One-shotsLookatthecircuitontheright:Condition#1:vIchangesfrom0toavoltjustbeforeG1invertsstate.voisnowoutput0volt.FindtherelationbetweenvI’andvIAslongasvI’

3、vIvalueatthispoint,denoteitasVT+,then=0Stablestate1Stablestate2Positivegoingswitchingthreshold上限触发电平2021/8/22Chapter7Latches,Flip-Flops,andTimers3DeterminetheHysterisisofaSchmittTriggerLecture25SchmittTrigger,One-shotsFindtherelationbetweenvI’andvIatcondition#2.Remembern

4、owvo=VDD=VDDVR1AsvIgoesdown,vI’alsogoesdown,whenvI’≤VGS(th)Gate1outputHIGH,gate2outputLOW,vo=0VFindvIvalueatthispoint,denoteitasVT-,thenNegativegoingswitchingthresholdtheHysterisis下限触发电平2021/8/22Chapter7Latches,Flip-Flops,andTimers4AnalysisofHysterisisWhenlocked,outputwa

5、veform？Lecture25SchmittTrigger,One-shotsSeedemoIn-phaseoutput2021/8/22Chapter7Latches,Flip-Flops,andTimers5SchmittTriggerApplicationLecture25SchmittTrigger,One-shots1.Waveformtransformation(波形变换)Invertedoutput2021/8/22Chapter7Latches,Flip-Flops,andTimers6SchmittTriggerAp

6、plicationLecture25SchmittTrigger,One-shots2.Pulserectification(脉冲整形)2021/8/22Chapter7Latches,Flip-Flops,andTimers7SchmittTriggerApplicationLecture25SchmittTrigger,One-shots3.Pulsemagnitudedetection(脉冲鉴幅)2021/8/22Chapter7Latches,Flip-Flops,andTimers81.BipolarICIntegratedS

7、chmittTriggerSolvefor：iC2≈2.2mA,iB2≈1.3mAHowmanyvoltsisVOL？Howtosolve?So，VOL=VCE(sat)2+vE2≈0.2V+1.7V=1.9VAns：VOL=VCE(sat)2+vE2，vE2isemittervoltagelevelwhenT2issaturatedvE2=R4(iB2+iC2)WhenvB1risetovB1+=vE2+0.7V=2.4V，T1startsturningon，throughpositivefeedbackT1getssaturated

8、quickly，T2quicklyturnsoff。Lecture25SchmittTrigger,One-shotsVCC2021/8/22Chapter7Latches,Flip-Flops,andTi