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1、附录A外文翻译theequivalentdcvalue.Intheanalysisofelectroniccircuitstobeconsideredinalatercourse,bothdcandacsourcesofvoltagewillbeappliedtothesamenetwork.Itwillthenbenecessarytoknowordeterminethedcandaccomponentsofthevoltageorcurrentinvariouspartsofthesystem.EXAMPL13.13Determinetheaveragevalueofthewaveform
2、sofFig.13.37.FIG.13.37Example13.13.Solutions:a. Byinspection,theareaabovetheaxisequalstheareabelowoveronecycle,resultinginanaveragevalueofzerovolts.b. UsingEq.:asshowninFig.13.38.Inreality,thewaveformofFig.13.37issimplythesquarewaveofFig. 13.37 with a dc shift of 4 V; that isv2=v1+4VFIG.13,8制.甘他FEEF
3、YZFIYtWpfor/q/77及1337EXAMPL13.14Findtheaveragevaluesofthefollowingwaveformsoveronefullcycle:a. Fig.13.39.b. Fig.13.40.FIG. 13.3Be而川卫the or。窗空 vaiue for 限、即的加0fM 工gSolutions:4 (3 V)(4 ms) 11 VX4 小勺 _ 12V- 4V 3L G = 8 ms=IVRote Fig 13.41b. G =(10V)(2 小助 4 (4 V)(2m0 - (2 V)(2 ms)10 ms-20V + gV-4V = _2V
4、 = _L6VNote Fig. 13.42dewlttaetei(benveeii0andms)FIG. 1341Um rponse cf a de msfer fo 加。咋即,昂nw of Fi 1339.de Jim-，: between C and 10 m 力FIG. 1342The response of a met to 加出 h/b浜射tw of 13.40.Wefoundtheareasunderthecurvesintheprecedingexamplebyusingasimplegeometricformula.Ifweshouldencounterasinewaveor
5、anyotherunusualshape,however,wemustfindtheareabysomeothermeans.Wecanobtainagoodapproximationoftheareabyattemptingtoreproducetheoriginalwaveshapeusinganumberofsmallrectanglesorotherfamiliarshapes,theareaofwhichwealreadyknowthroughsimplegeometricformulas.Forexample,theareaofthepositivepulseofasinewave
6、is2Am.Approximatingthiswaveformbytwotriangles,weobtainusingarea1/2baseheightfortheareaofatrianglearoughideaoftheactualarea:Acloserapproximationmightbearectanglewithtwosimilartriangles:=2.094Jwwhichiscertainlyclosetotheactualarea.Ifaninfinitenumberofformswereused,anexactanswerof2Amcouldbeobtained.For
7、irregularwaveforms,thismethodcanbeespeciallyusefulifdatasuchastheaveragevaluearedesired.Theprocedureofcalculusthatgivestheexactsolution2Amisknownasintegration.Integrationispresentedhereonlytomakethemethodrecognizabletothereader;itisnotnecessarytobeproficientinitsusetocontinuewiththistext.Itisauseful
8、mathematicaltool,however,andshouldbelearned.Findingtheareaunderthepositivepulseofasinewaveusingintegration,wehavewherefisthesignofintegration,0andparethelimitsofintegration,Amsinaisthefunctiontobeintegrated,anddaindicatesthatweareintegratingwithrespecttoa.Integrating,weobtainArea = -cos ac- 3河(com t
9、 - cos 00)=一且/一1 一十 D =Q3.L)Sinceweknowtheareaunderthepositiveornegativepulse,wecaneasilydeterminetheaveragevalueofthepositiveornegativeregionofasinewavepulsebyapplyingEq.13.26:ForthewaveformofFig.13.45,EXAMPLE13.15DeterminetheaveragevalueofthesinusoidalwaveformofFig.13.46.Solution:Byinspectionitisf
10、airlyobviousthattheaveragevalueofapuresinusoidalwaveformoveronefullcycleiszero.Eq.(B.26):+2-?=-一吗=0V27r13.47.EXAMPL13.16DeterminetheaveragevalueofthewaveformofFig.Solution:Thepeak-to-peakvalueofthesinusoidalfunctionis16mV+2mV=18mV.Thepeakamplitudeofthesinusoidalwaveformis,therefore,18mV/2=9mV.Counti
11、ngdown9mVfrom2mVresultsinanaverageordclevelof-7mV,asnotedbythedashedlineofFig.13.47.EXAMPLE13.17DeterminetheaveragevalueofthewaveformofFig.13.48.Solution:EXAMPLE13.18ForthewaveformofFig.13.49,determinewhethertheaveragevalueispositiveornegative,anddetermineitsapproximatevalue.Solution:Fromtheappearan
12、ceofthewaveform,theaveragevalueispositiveandinthevicinityof2mV.Occasionally,judgmentsofthistypewillhavetobemade.InstrumentationThedcleveloraveragevalueofanywaveformcanbefoundusingadigitalmultimeteroranoscilloscope.Forpurelydccircuits,simplysettheDMMondc,andreadthevoltageorcurrentlevels.Oscilloscopes
13、arelimitedtovoltagelevelsusingthesequenceofstepslistedbelow:1. FirstchooseGNDfromtheDC-GND-ACoptionlistassociatedwitheachverticalchannel.TheGNDoptionblocksanysignaltowhichtheoscilloscopeprobemaybeconnectedfromenteringtheosc川oscopeandrespondswithjustahorizontalline.Settheresultinglineinthemiddleofthe
14、verticalaxisonthehorizontalaxis,asshowninFig.13.50.(a)FIG.UMUsingtheoscrlloopero删绅devo/ragw:serrmg密eGXDen而ioir;Z也1v&rncctlsfiiflresnt。?医力心推arfci心口息止m力部，通姓百ihDCoprion.2. Applytheosc川oscopeprobetothevoltagetobemeasured,andswitchtotheDCoption.Ifadcvoltageispresent,thehorizontallinewillshiftupordown,asd
15、emonstratedinFig.13.50.Multiplyingtheshiftbytheverticalsensitivitywillresultinthedcvoltage.Anupwardshiftisapositivevoltage,whileadownwardshiftisanegativevoltage.Ingeneral,%=(verticalindivJX(vlical牌口疝witymVdm)ForthewaeformofFig.U.SOfb),%=(2.5div,)(50mV,div.)=125mVTheoscilloscopecanalsobeusedtomeasurethedeoraveiag
