LAB 3: DC Simulations and Circuit Modeling - utdallas.edu · card) for simulation. Lab 3: DC Simulations 3

ADS Fundamentals – 2009

LAB 3: DC Simulations and Circuit Modeling

Overview‐Thischapterintroducesparametricsubnetworks:howtocreateandusetheminhierarchicaldesigns.Beginningwithadevicemodel,thelowestlevelsubnetworkwillalsocontainpackagingparasiticstobettermodelthedevicebehavior.Also,atesttemplatewillbeusedtosimulatecurvetracerresponsesfromwhichabiasnetworkcanbecomputed,built,andchecked.Thecircuitinthislabexercisewillbethefoundationoftheamplifierthatwillbeusedfortheotherlabexercisesinthiscourse.

OBJECTIVES • ModelagenericBJTwithparasiticsandsaveitasasubcircuit.

• SetupandrunnumerousDCsimulationstodetermineperformance.

• Calculatebiasresistorvaluesinthedatadisplay.

• BuildabiasednetworkbasedontheDCsimulations.

• Testthebiasednetwork.

©CopyrightAgilentTechnologies2009

Lab 3: DC Simulations

3‐2 ©CopyrightAgilentTechnologies2009

Table of Contents

1. Create a new project: amp_1900. ........................................................................3

2. Set up a generic BJT symbol and model card. ....................................................3

3. Add parasitics and connectors to the circuit.........................................................6

4. View the default symbol. ......................................................................................7

5. Define the symbol and artwork in Design Parameters. ........................................7

6. Use a curve tracer template to test the bjt_pkg sub-circuit. .................................9

7. Modify the template Parameter Sweep. .............................................................11

8. Simulate at beta=100 and 160. ..........................................................................11

9. Open a new design and view the project in the Main window............................12

10. Set up and simulate the dc bias parameter sweep. ........................................14

11. Calculate bias values Rb and Rc for a grounded-emitter circuit. ....................15

12. Set up the biased network. .............................................................................16

13. Simulate and annotate the DC solution. ........................................................17

14. OPTIONAL: Sweep Component Model Temperatures ...................................18


33‐3©CopyrightAgilentTechnologies

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PROCEDUREThecircuityoubuildforthislabexercisewillbeusedasthelowerlevelsub‐circuitforalloftheamplifierlabstofollow.1. Createanewproject:amp_1900.

a. Ifyouhavenotalreadycreatedthisproject,doitnow.Then,inthisnewproject,amp_1900,openanewschematicwindowandsaveitwiththename:bjt_pkg.Also,setanydesiredOptions>Preferences.

2. SetupagenericBJTsymbolandmodelcard.

a. Intheschematicwindow,selectthepalette:Devices–BJT.SelecttheBJT_NPNdeviceshownhereandinsertitontotheschematic.

b. InserttheBJT_Model(modelcard)shownhere.

c. DoubleclickontheBJT_Modelcard.Whenthedialogappears,clickComponentOptionsandinthenextdialog,clickClearAllforparametervisibility–thenclickApply.ThiswillremovetheGummel‐Poonparameterlistfromtheschematic.Keepthisdialogopen.

NOTEonBinning:YoucaninsertmultiplemodelcardsandusetheBinModelcomponenttovarythemodeldevicevariations.Thesevariationscanbeparameterssuchastemperature,lengthorwidth.TheBinningcomponentallowsyoutocreateamatrixthatreferencesthedesiredmodels.

NOTE:TheBJT_NPNsymbolshowsModel=BJTM1.Thismeansthesymbolwillusethatspecificmodel(modelcard)forsimulation.



d. Next,inBJT_Modeldialog,selecttheBfparameterandtypeinthewordbetaasshownhere.Also,clickthesmallbox:DisplayparameteronschematicforBfonlyandthenclickApply.Betaisnowaparameterofthiscircuit–lateronyouwilltuneitlikeavariable.

e. SetVaf(ForwardEarlyVoltage)=50anddisplayit.

f. SetIse(E‐Bleakage)=0.02e12,anddisplayit.ThenclosethedialogdialogwithOK.Thedevicenowhassomemorerealisticparameters.parameters.

g. FortheBJT_NPNdevicesymbol,removetheunwanteddisplayparameters(Area,Region,TempandMode)byuncheckingthebox.Thisbox.Thiswillmaketheschematiclesscrowdedwithtext.

Clickheretodisplayanindividualvalue.

UseComponentOptionstoclearallthedisplayedparameters.



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3. Addparasiticsandconnectorstothecircuit.

Thepictureshownhereisthecompletedsub‐circuitwithconnectorsandparasitics.Remembertousetherotateiconfororientationofthecomponentsasyouinsertthem.Herearethesteps:

a. InsertlumpedLandCcomponents:Insertthreeleadinductorsof320pHeachandtwojunctioncapacitorsof120fFeach.Besuretousethecorrectunits(picoandfemto)oryourcircuitwillnothavethecorrectresponse.Tip:typeLorCincomponenthistorytogetthecomponentsontoyourcursorwithoutusingthepalette.

b. AddsomeresistanceR=0.01ohmstothebaseleadinductoranddisplaythedesiredcomponentvaluesasshown.

c. Insertportconnectors:Clicktheportconnectoricon(shownhere)here)andinserttheconnectorsexactlyinthisorder:1)collector,collector,2)base,3)emitter.YoumustdothissothattheconnectorsconnectorshavetheexactsamepinconfigurationastheADSBJTBJTsymbol.

d. Edittheportnamesasshowhere:changeP1toC,changeP2toB,andchangeP3toE.

e. Cleanuptheschematic:Positionthecomponentssothattheschematicisorganized–thisisgoodpractice.Tomovecomponenttext,presstheF5key,selectthecomponent,andpositionthetextusingthecursor.

NOTE:Numbertheports(num=)exactlyasshownorthedevicewillnothavethecorrectorientationforthesymbolthatwillbecreated.



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Defaultsymbol

4. Viewthedefaultsymbol.

Therearethreewaystocreateasymbolforacircuit:1)usethedefaultsymbol,2)drawasymbol,or3)useabuilt‐insymbol.Forthislabyouwilluseabuilt‐inBJTsymbol.Thefollowingstepsshowhowtodothis:

a. Toseethedefaultsymbol,click:View>Create/EditSchematicSymbol.WhentheSymbolGeneratordialogappears,clickOKandthedefaultsymbolwillappear.

b. Next,aboxorrectanglewiththreethreeportsisgenerated:defaultsymbol.However,deletethissymbolsymbolusingthecommands:SelectSelect>SelectAll.Thenclickthethetrashcaniconordeletekey.key.

c. Returntotheschematic‐click:Viewclick:View>Create/EditSchematic.

5. DefinethesymbolandartworkinDesignParameters.Parameters.

a. ClickFile>DesignParametersandthedialogappears

b. IntheGeneraltab,maketheseschanges:1)changetheComponentInstanceNametoQ,2)changetheSymbolNametoSYM_BJT_NPNbyclickingthearrowandselectingit(thisisthebuilt‐insymbol),3)inthe

Built‐insymbol:SYM_BJT_NPN

SOT23fixedartwork



Artworkfield,selectFixedandSOT23asshownhere.

c. ClickSaveAELFiletowritethesechangesbutdonotclosethisdialogyetbecauseyoustillneedtosetotherparameters.

d. GototheParameterstab.IntheParameterNamearea,typeinbetaandassignadefaultvalueof100byclickingtheAddbutton.BesuretheboxtoDisplaytheparameterischeckedasshownhere.ClicktheOKbuttontosavethenewdefinitionsanddismissthedialog.

e. Intheschematicwindow,Savethedesign(clicktheiconshownhere)tomakesureallyourworkcreatingthissub‐circuitwillnotbelost.Inthenextsteps,youwillseehowtheDesignParameterswillbeused.

Theparameterbetaisnowrecognizedasavariableofthiscircuit.Itsvaluecannowbepassed(assigned)fromanupperlevelhierarchywhenyouusebjt_pkgasasub‐circuit.

NOTES:multiplicity_M

Youcandefinemultiplecomponentsinparallel.Youcanalsocopyparametersfromanotherdeviceorfile.



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6. Useacurvetracertemplatetotestthebjt_pkgsubcircuit.

a. Inthecurrentschematicofthebjt_pkg,clickFile>NewDesign.Whenthedialogappears,typeinthename:dc_curvesandselecttheBJT_curve_tracertemplateasshown.ClickOKandanewschematicwillbecreatedwiththetemplate,readytoinsertbjt_pkg.

Thisisadatadisplaytemplate–itwillautomaticallyplotthecurves.

Thisiswhereyouwillconnectthedevice(bjt_pkg)inthenextfewsteps.



b. SavethedesignandthenclicktheComponentLibraryicon(shownhere).

c. Whenthedialogopens,selectProjects>Amp1900andthenclickanddragthebjt_pkgintotheschematicandinsertitasshownhere.Everycircuitthatyoubuildwillbeavailableintheprojectlibraryasasub‐circuit.

d. Connectthebjt_pkgcomponentasshown.Youmayhavetoadjustthewiresandtext(F5)tomakeitlookgood.Also,youcannowclosethelibrarywindowandsavethedc_curvesdesignagain‐itisgoodpracticetosavedesignsoften.

NOTEontemplates:Youcanalsoinserttemplatesusingtheschematicwindowcommand:Insert>Template.Manytemplateshavepre‐definedvalues,nodenames(wirelabels),andvariables.Therefore,youmayhavetomakemodificationstofityourcircuit.Also,manyofthesetemplateshavedatadisplaytemplatesthatautomaticallyplotthedatainapre‐definedformat.Thesesamedatadisplaytemplatesareavailableinthedatadisplaywindow.Ingeneral,usingtemplatesisveryefficientandtimesavingifyouknowhowtouseADS.



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DCCurvesatbeta=100

7. ModifythetemplateParameterSweep.

a. ChangetheParameterSweepIBBvaluesto:0uAto100uAin10uAstepsasshownhere.DonotchangetheDCsimulationcontrollerdefaultsettingsforsweepingVCE–theyareOK.NoticethattheVAR1variables(VCE=0andIBB=0)donotrequiremodificationbecausetheyareonlyrequiredtoinitialize(declare)thevariableforthesimulator.

8. Simulateatbeta=100and160.

a. Simulate(F7)withBeta=100.Afterthesimulationisfinished,thedatadisplaywillwillappearwiththecurvetracerresults(data(datadisplaytemplate).Trymovingthemarkermarkerandwatchtheupdatedvaluesappear.appear.

b. SimulateagainwithBeta=160bychangingchangingthevaluedirectlyontheschematic.Youshouldseetheupdatedvalues.

c. Verifythevaluesforbeta=160andVCE=3V,whereIBB=40uAandIC=3mAwithabout10mWofconsumedpowerIfnot,checkthedesign.

Parametersweepusedformultiplevariablesweeps.NotethatDC1isthename(SimInstanceName)ofthesimulationcontroller.

Onlyonevariablecanbesweptinthecontroller.

VarEqnisrequiredtoinitializevariables.



StartupandWorkingdirectoryicons:

HideandShowicons:

9. OpenanewdesignandviewtheprojectintheMainwindow

a. Savethecurrentschematic:dc_curves.Inthesamewindow,createanewdesign(withoutatemplate)named:dc_bias.ThensavethedesignbyclickingontheSaveCurrentDesignicon(shownhere)sothatitiswrittenintotheADSdatabase.

b. Also,savetheDataDisplay.

c. GototheADSMainwindowandverifythatyourprojecthasthreedesignsandthedatadisplayasshownintheProjectView.

d. Also,lookattheFileViewtoseetheDatadirectorywherethesimulationdatasetsarewritten.Clickonthe+toexpandthedirectoryfolderand–tocloseit.Andthenlookinthenetworksdirectoryfolder–thisiswheretheschematicdesigns(.dsn)arewritten.

e. ClickontheFileViewandthenthetheProjectViewtabs‐noticethatthethatthetoolbariconschange.

f. IntheFileViewtabmode,clickthetheiconsforStartupandWorkingdirectorytodirectorytoseehowtheywork.Youwork.Youcanalwaysbrowsethethefilesofanydirectoryandcomecomebacktoyourworkingdirectory,suchasamp_1900.amp_1900.

g. AlsotrytheHideandShowicons.

Datasetsareinthedatafolder,andschematicdesignsareinthenetworksfolder.



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10. Setupandsimulatethedcbiasparametersweep.

NOTEonparametersweeps:Ifonlyonevariableisswept,youcanusetheSimulationcontroller(Sweeptab).However,ifmorethanoneparameterisswept,aParametersweepcomponentisrequiredasinthetemplatesyouhavejustused.Ingeneral,allsimulationcontrollersallowyoutosweeponlyoneparameter(variable).

BUILDthecircuitwithoutatemplate‐thestepsfollow:

a. Insertthebjt_pkgusinglibraryiconorthecomponenthistory.Nowpushintothebjt_pkgandclickFile>DesignParameters.Resetthebetaparameterdefaultto160,popoutanddeletethebjt_pkgandreinsertit–betaisnow160wheneveryouusethemodeledcircuit.

b. FromtheProbecomponentspaletteorcomponenthistory,insertanI_ProbeandrenameitICinsteadofI_Probe1asshownhere.YoucanalsogetthecurrentfromthesimulationbysettingtheDCcontrollerOutputtabforPinCurrentsbuttheprobeiseasytouseinthiscase.

c. FromtheSourcesFrequencydomainpaletteorusingcomponenthistory,insertadcsupplyandcurrentsourceandsettheirvaluesasshown:Vdc=3VandIdc=IBBasshownhere.

d. Wirethecomponentstogetherandaddtheground(groundicon).

e. InsertaDCsimulationcontroller(DC).Edit(doubleclick)thecontrollerandgototheSweeptabandassign:IBB:10uAto100uAin10uAsteps(besuretouseuAunitsbecausethesweeptabisgeneric).ThengototheDisplaytabandcheckthesettingstobedisplayedasshown.ThenclickApplyandOK.



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f. InsertaVAR(clickicon)variableequation.UsethecursoronthescreentosetIBB=0Atoinitialize(declare)thevariabletobeswept.

g. InsertawirelabelVBEatthebase.Thevoltagesatthatnodewillappearinthedatasetforuseincalculatingbiasresistorvalues.

h. Simulateandplotthedata.Whenthedatadisplayopens,insertalistofVBEandIC.ionly.BecauseyousweptIBBtogetthesevalues,IBBwillautomaticallybeincluded.

NOTEonresults:Asyoucansee,with3voltsacrossthedevice,40uAofbasecurrentresultsinabout799mVacrossthebase‐emitterjunction,withabout3.3mAofcollectorcurrent.Ifyouwant,drawaboxaroundthevaluesat40uAIBB.

i. Savethedesignanddatadisplay.

11. CalculatebiasvaluesRbandRcforagroundedemittercircuit.

a. Inthedatadisplay,insertanequationandtype:Rb=(3–VBE)/IBB.

b. SelecttheRbEqnandusethekeyboardCtrlCandCtrlVtocopy/pasteit–itwillbecomeRb1.

c. HighlighttheRb1equationasshownandchangeittobecomeRc:Rc=2/IC.i.ThetotalDCsupplywillbe5volts.Therefore,with3voltsVCE,2voltsremainforthecollectorresistor.

d. InsertanewListandscrolldowntotheEquationsmenu(shownhere),andaddRbandRc.Theneditbothcolumnheadingsonthelistwithabracketed[3]asshown.Thisreferencesthe40uAIBBusingitsindexvalue[3].Indexvaluesbeginatzero:0,1,2,3,etc.YoucanalsousePlotOptionstoaddalabeltothelistasshown:



12. Setupthebiasednetwork.

Nowthatyouhavethecalculatedbiasresistorvalues,youcantestthebiasnetwork.

a. Savethedesign(dc_bias)withanewname:dc_net.Bythistime,youshouldknowhowtodothis(File>SaveDesignAs).Also,saveandclosethedc_biasdatadisplay.

b. Modifythedesignasshown.BeginbydeletingthecurrentsourceIBB,theI_Probe,andtheVarEqn.

c. GototheLumpedComponentspaletteorusecomponenthistory,R,toinsertresistorsforthebase(56kOhm)andcollector(590Ohm)resistorsasshown.Youmayneedtouserotatetoinsertitcorrectly.

d. ChangetheinstanceRnamestoRCandRBasshown.

NOTEoncomponentswithartwork:Lateron(afterthelastlab),youcaneasilyandquicklychangetolumpedcomponentswithartworkbychangingthecomponentname–forexample,changeRtoR_Pad1,CtoC_Pad1,LtoL_Pad1,etc.Thenyoucancreatealayoutoftheschematic.Fornow,uselumpedwithoutartwork.

e. SettheV_DCsupply:Vdc=5V.Wirethecircuitandorganizeit.

f. DeletetheDCsimulationcontrollerandputanewoneinitsplace–thisisfasterandmoreefficientthanremovingthesweepsettings.Becausethereisnosweep,youdonothavetosetanythingtocheckDCvalues.

InsertthecursorandtypeovertorenameittoRC.



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13. SimulateandannotatetheDCsolution.

a. UsetheSimulate>SimulationSetup(orHotKeyHotKey“S”ifyouhavesetit)andunchecktheboxtheboxtoopendatadisplayaftersimulation.simulation.

b. ClickSimulate>Simulate,oronaPCtrytheF7keyboardkey,torunthesimulation.Thedatasetnamewillbethesameastheschematic–thisisthedefault.Youcanverifythisbyreadingthestatuswindow:

c. Annotatethecurrentandvoltagebyclickingonthemenucommand:Simulate>AnnotateDCSolution.Ifnecessary,movecomponentsorcomponenttext(F5key)toclearlyseethevaluesofvoltageandcurrent.Besurethatyouhavethesamevaluesshownhere.Ifnot,checkyourwork,includingthesub‐circuit.

NOTE:Nodenames(pin/wirelabels)suchasVCorVBEcanbemovedbydraggingthemwithyourcursor.



d. Cleartheannotation,click:Simulate>ClearDCAnnotationandthenSaveallyouwork.Closeallwindowsifnordoingtheoptionalstepsthatfollow.

14. OPTIONAL:SweepComponentModelTemperatures

a. EdittheDCcontroller–selectitandclicktheediticon.

b. IntheSweeptab,entertheADSglobalvariabletemp(defaultisCelsius)andenterthesweeprange:55to125withstepsize=5.Also,intheDisplaytab,clicktheboxestodisplaytheannotationonthecontroller–clickApplytoseeitandOKtodismissthedialog.

c. InsertVCandVBEnode/pinlabels.

d. Setthesimulationdatasetnametodc_temp,andandchecktheboxtoopenthedatadisplaydc_net.dc_net.ClickApplyandthenSimulate.

NOTE:TheTriseparameter(temperatureriseoveroverambient)canbespecifiedonindividualcomponents.



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e. PlotVCandVBEinarectangularrectangularplot.Thesewillbevs.bevs.tempwhichisthesweptvariable.YoucouldalsousetheAddtheAddVsfunctionbutitisnotnotnecessarywhenthereisoneonesweptvariable.

f. Puttwomarkersoneachtraceindeltamodetoseethechangeinvoltageastemperaturechanges.Theplotshouldlookliketheoneshownhere:collectorvoltagedecreasesatalmostone‐halftherateofVBEasthetemperatureincreases.Youcanusethistemperaturesweepmethod(sweepingtheglobalvariable“temp’)foranyADSsimulation.

EXTRA EXERCISES:

1. Plotcurrent(probe:IC.i)vs.temperatureusingaprobe.Or,trysettingupapassedparameterfortemperature(Temp=25intheoptionscontroller).TheOptionscontrollerisineverysimulationpaletteandcanbeusedtosetconvergenceforDCandconstantsimulationtemperature.

2. ReplacetheGummel‐Poonmodelcardwithanothermodel(Mextram)andresimulate.Afterward,comparetheresults.

3. InsertthetemplateSP_NWA_TwhichgeneratesS‐parametersforabjtatallthespecifiedbiaspoints.Tryusingthiswithyourbjt_pkg.



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LAB 3: DC Simulations and Circuit Modeling - utdallas.edu · card) for simulation. Lab 3: DC Simulations 3