the non–inverting buffer：非–反相缓冲器

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1、TheNon–InvertingBufferWenowspendsometimeinvestigatingusefulcircuitelementsthatdonotdirectlyimplementBooleanfunctions.Thefirstelementisthenon–invertingbuffer.ThisislogicallyequivalenttotwoNOTgatesinarow.Thereareengineeringdifferencesbetweenthetwo,mostnotablythatthenon–invertingbufferdelayst

2、hesignallessthanachainoftwoNOTgates.Thisisbestconsidereda“voltageadjuster”.Alogic1(voltageintherange2.0–5.0volts)willbeoutputas5.0volts.Alogic0(voltageintherange0.0–0.8volts)willbeoutputas0.0volts.GateDelaysTheoutputofacircuitelementdoesnotchangeinstantaneouslywiththeinput,butonlyafteradel

3、aytimeduringwhichthecircuitprocessesthesignal.Thisdelayinterval,called“gatedelay”isabout10nanosecondsformostsimpleTTLcircuitsandabout25nanosecondsforTTLFlip–Flops.ThesimplestexampleistheNOTgate.Hereisatraceoftheinputandoutput.Notethattheoutputdoesnotreflecttheinputuntilonegatedelayafterthe

4、inputchanges.ForonegatedelaytimewehavebothX=1andY=1.DelayCircuitsForsomeadvanceddesigns,itisdesirabletodelayasignalbyafixedamount.OnesimplecircuittoachievethiseffectisbasedontheBooleanidentity.Acircuittoimplementthisdelaymightappearasfollows.Hereisthetimetraceoftheinputandoutput.ThePulseGe

5、neratorThiscircuitrepresentsoneimportantapplicationofthegatedelayprinciple.Weshallpresentthiscircuitnowanduseitwhenwedevelopflip–flops.Thiscircuit,whichIcalla“pulsegenerator”,isbasedontheBooleanidentity.HereisthecircuitHereisatimeplotofthecircuit’sbehavior.Thepulseisduetothefactthatfor1gat

6、edelay,wehavebothX=1andY=1.ThisisthetimeittakestheNOTgatetorespondtoitsinputandchangeY.TheTri–StateBufferSometimeago,weconsideredrelaysasautomaticswitches.Thetri–statebufferisalsoanautomaticswitch.Herearethediagramsfortwoofthefourmostpopulartri–statebuffers.Anenabled–lowbufferisthesameasan

7、enabled–highbufferwithaNOTgate.Whatdoesatri–statebufferdowhenitisenabled?Whatdoesatri–statebufferdowhenitisnotenabled?Whatisthisthirdstateimpliedbythename“tri–state”?AnEnabled–HighTri–StateBufferConsideranenabled–hightri–statebuffer,withtheenablesignalcalled“C