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1、Model,Measure,RepeatObjectiveInthislabwe’llbeexploringoneofthestrategiesengineersusetoexplorethephysicalworld.Asatooltohelpusexplorewe’llbeworkingwithanewcategoryofelectronicdevice,thesemiconductordiode.It’sbehaviorisalittledifferentfromtheothercircuitdevicesyou’vebecomeusedtoworkingwith.Engi
2、neersandscientistsoftenusemathematicalmodelstopredictthebehaviorofphysicalsystems.We’llbeusingMatlabtodescribethebehaviorofourdiodes.Otherengineerswillembedthosemathematicalmodelsintomoreusefulformstosimulatemorecomplexsystems.Inordertobesurethemodelcorrectlypredictsthesystem’sbehavior,carefu
3、lmeasurementsaretaken.Differencesbetweenthetheoreticalpredictionsandactualperformancehavetobeaccountedfor,explained,andhopefullybuiltintothemodelforthenextiteration.We’regoingtofollowthispathonthisexperimentandseewhatdevelops.Asimpledescriptionofadiodeisthatitisadevicethatletscurrentflowinonl
4、yonedirection.TheprelabrequirestheuseofMatlabtoobtainadiodeI(current)vs.V(voltage)curve.Inlab,you’lluseafunctiongeneratorandoscilloscopetoobservethebehaviorofadiodecircuit.Then,you’llexperimentallydetermineitsIvs.Vcurve.You’llalsousePSpicetosimulatethesamecircuits,andagainobtainaplotofthecurr
5、entthroughthediodeversusthevoltageacrossthediode.Theseplotswillthenbecomparedtoeachotherandmanufacturer’sdata,andyou’llincludethecomparisonsinalabreport.Asyouworkthroughthislab,keeptheMETHODinmind.ConceptsAdiodeallowscurrenttoflowonewayandnottheother.IfweconsiderthecircuitshowninFigure1,wecan
6、seeavisualexplanationofthis.Figure1:SeriesDiodeCircuitLet’sassumetheinputofthecircuitisthesinusoidshowninFigure2.We’llalsoassumethediodeisanidealdiode,whichturnson(allowscurrenttopassthroughit)at0V,andexhibitsnovoltagedropwhencurrentpassesthroughit.Thediodeonlyallowspositivecurrenttoflow,sone
7、gativecurrentwillbezero.Thus,ifweplotthecircuitoutputacrossR2,wegettheresultinFigure3.Thepositivevoltagesareshown,butthenegativevoltagegetscuttozero,sincecurrentcan’tflowinanegativedirection.TheoutputshowninFigure3istheresultofacircuitcalleda