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Circuit simulation



Introduction

Electroniccircuitsimulation(English:Electroniccircuitsimulation),referstotheuseofmathematicalmodelstoverifytherealityofelectroniccircuitsTheengineeringmethodofbehaviorsimulation.

Thesimulationsystemcansimulatethefunctionalbehaviorofthecircuitwithouttheneedtobuildtheactualcircuit(thisprocessmaybecumbersomeandexpensive),soitisaverypracticaltool.Asthesimulationsystemsimulatestherealsituationmoreandmorerealistically,manyuniversitiesandresearchinstitutionswillusesuchtoolstoassisttheteachingofelectronicengineering.Sinceelectroniccircuitsimulationsystemsgenerallyhavebettergraphicalinterfaces,theycanoftenmakeusersfeelimmersive.Forbeginners,theycananalyze,synthesize,organizeandevaluatewhattheyhavelearnedwiththehelpofsimulationsoftware.

Beforeconstructingtheactualcircuit,simulationandverificationofthedesigncangreatlyimprovethedesignefficiency.Thisisbecausethedesignercanobserveandstudythebehaviorofthecircuitinadvancebeforeconstructingthecircuit,withouthavingtopaytimeandeconomiccostsforthephysicalrealizationofthecircuit.Especiallyforintegratedcircuits,thecostofelectronicprocessessuchasphotomasksrequiredtophysicallyimplementcircuitsisexpensive,andthehighcomplexityofintegratedcircuitsisdifficulttoachieveonbreadboards,anditisdifficulttostudythebehaviorofcircuitsusingtraditionalmethods.Therefore,almostallintegratedcircuitdesignsrelymoreonsimulation.ThemostfamousanalogsimulationisSPICE,andthemostfamousdigitalcircuitsimulatorsarebasedonVerilogorVHDL.

Someelectronicsimulationsystemsintegrateschematiceditors,simulationengines,andwaveformdisplayfunctions,sothatuserscaneasilyobservethereal-timestateofcircuitbehavior.Usually,thesimulationsystemwillalsoincludeextendedmodelsandelectroniccomponentlibraries.Themodelsmainlyincludetransistormodelsdedicatedtointegratedcircuits,suchasBSIM;andthecomponentlibrarywillprovidemanycommoncomponents,suchasresistors,capacitors,inductivecomponents,transformers,anduser-definedmodels(suchascontrolledcurrentsourcesandvoltagesources).Inaddition,somemodelsinVerilog-AorVHDL-AMScanbeprovided).Printedcircuitboarddesignalsorequiresspecialmodels,suchastransmissionlinemodelsandIBISmodelsforlinerouting.

Type

Althoughtherearestrictanalogsignalelectroniccircuitsimulators,mostsimulatorsincludebothanalogandevent-drivendigitalsimulators.Theyareoftencalledmixed-modesimulators.Thismeansthatmostsimulationsystemsincludeanaloganddigitalcomponents.Inthisway,mixedsignalprocessingcanbedoneonthesameintegratedschematic.Inthemixed-modesimulationsystem,thedigitalmodeprovidesaccuratespecificationsfortiming,risingedge,andfallingedgedelay.

Themixedmodesimulatorprovidesevent-drivenalgorithmsandsupportsnon-digitaldata.Forexample,realnumbersandintegerscanbeusedtosimulatethefunctionsofadigitalsignalprocessorordatasamplingfilter.Becauseevent-drivenalgorithmsarefasterthanstandardSPICEmatrixsolutions,usingevent-drivenalgorithmstoreplaceanalog-typemodelscansavetime.

Mixedmodesimulationisdividedintothefollowingthreelevels:

  1. Digitallogicsimulatorusingoriginaldigitalelementsandtimingmodels

  2. Usingthesub-circuitmodeloftheactualtransistortopologyoftheintegratedcircuit

  3. Usinglogicalalgebraicexpressions

Intheanalysisofthetransmissionlinemodelandsignalintegrity,itisnecessarytocarefullycheckthenatureoftheinputandoutputportsoftheintegratedcircuit.Atthistime,accuratecircuitdescriptionsshouldbeused.Logicalgebraicexpressionsdonothaveatimedelayfunction.Inananalogenvironment,theycanprovideprocessingoflogicsignals.ThesetwomodelsuseSPICEtosolvetheproblem,whileinthethirdmethod,ahybridmodelofthesimulatorisused.Eachoftheabovemethodshasitsownadvantagesandissuitablefordifferentapplications.Infact,manysimulationsystems(especiallythoseinvolvinganalog-to-digitalanddigital-to-analogconversion)requiretheintegrationofvariousmethods,andasingleapproachisnotenoughtosolvetheproblem.

Anothertypeofsimulationismainlyaimedatpowerelectronicstechnology,whichhasapiecewiselinearalgorithmmodel.

Complexity

Inthemanufactureofsiliconintegratedcircuits,duetothelevelofcraftsmanship,theremaybeacertaindeviationbetweenitselectricalpropertiesandthenominalvalue,andcircuitsimulatorsoftendonotConsiderthesedeviationsinactualsiliconintegratedcircuits.Thedeviationoftheseparametersmaybesmall,butoftenaccumulatedintheentirecircuitwillseriouslyaffecttheoutputofthechip.

Temperaturecanalsocausedeviation,buttherearesometechniquesthatcanmodeltheeffectoftemperature,allowingdesignerstocheckitsperformanceatdifferenttemperatureswhensimulatingthecircuit.

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