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ADS Fundamentals – 2009 LAB 3: DC Simulations and Circuit Modeling Overview ‐ This chapter introduces parametric subnetworks: how to create and use them in hierarchical designs. Beginning with a device model, the lowest level subnetwork will also contain packaging parasitics to better model the device behavior. Also, a test template will be used to simulate curve tracer responses from which a bias network can be computed, built, and checked. The circuit in this lab exercise will be the foundation of the amplifier that will be used for the other lab exercises in this course. OBJECTIVES Model a generic BJT with parasitics and save it as a sub circuit. Set up and run numerous DC simulations to determine performance. Calculate bias resistor values in the data display. Build a biased network based on the DC simulations. Test the biased network. © Copyright Agilent Technologies

# LAB 3: DC Simulations and Circuit Modelingrmh072000/Site/Software_and_Links_files/3B_lab.pdf · Simulate and annotate the DC solution ... Lab 3: DC Simulations ... draw a symbol,

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LAB 3: DC Simulations and Circuit Modeling

OBJECTIVES ModelagenericBJTwithparasiticsandsaveitasasubcircuit.

SetupandrunnumerousDCsimulationstodetermineperformance.

BuildabiasednetworkbasedontheDCsimulations.

Testthebiasednetwork.

• Lab 3: DC Simulations

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

• Lab 3: DC Simulations

2009

PROCEDUREThecircuityoubuildforthislabexercisewillbeusedasthelowerlevelsubcircuitforalloftheamplifierlabstofollow.1. Createanewproject:amp_1900.

2. SetupagenericBJTsymbolandmodelcard.

a. Intheschematicwindow,selectthepalette:DevicesBJT.SelecttheBJT_NPNdeviceshownhereandinsertitontotheschematic.

b. InserttheBJT_Model(modelcard)shownhere.

c. DoubleclickontheBJT_Modelcard.Whenthedialogappears,clickComponentOptionsandinthenextdialog,clickClearAllforparametervisibilitythenclickApply.ThiswillremovetheGummelPoonparameterlistfromtheschematic.Keepthisdialogopen.

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

• Lab 3: DC Simulations

d. Next,inBJT_Modeldialog,selecttheBfparameterandtypeinthewordbetaasshownhere.Also,clickthesmallbox:DisplayparameteronschematicforBfonlyandthenclickApply.Betaisnowaparameterofthiscircuitlateronyouwilltuneitlikeavariable.

e. SetVaf(ForwardEarlyVoltage)=50anddisplayit.

f. SetIse(EBleakage)=0.02e12,anddisplayit.ThenclosethedialogdialogwithOK.Thedevicenowhassomemorerealisticparameters.parameters.

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

Clickheretodisplayanindividualvalue.

UseComponentOptionstoclearallthedisplayedparameters.

• Lab 3: DC Simulations

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• Lab 3: DC Simulations

Thepictureshownhereisthecompletedsubcircuitwithconnectorsandparasitics.Remembertousetherotateiconfororientationofthecomponentsasyouinsertthem.Herearethesteps:

d. Edittheportnamesasshowhere:changeP1toC,changeP2toB,andchangeP3toE.

e. Cleanuptheschematic:Positionthecomponentssothattheschematicisorganizedthisisgoodpractice.Tomovecomponenttext,presstheF5key,selectthecomponent,andpositionthetextusingthecursor.

NOTE:Numbertheports(num=)exactlyasshownorthedevicewillnothavethecorrectorientationforthesymbolthatwillbecreated.

• Lab 3: DC Simulations

2009

Defaultsymbol

4. Viewthedefaultsymbol.

Therearethreewaystocreateasymbolforacircuit:1)usethedefaultsymbol,2)drawasymbol,or3)useabuiltinsymbol.ForthislabyouwilluseabuiltinBJTsymbol.Thefollowingstepsshowhowtodothis:

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

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

c. Returntotheschematicclick:Viewclick:View>Create/EditSchematic.

5. DefinethesymbolandartworkinDesignParameters.Parameters.

a. ClickFile>DesignParametersandthedialogappears

b. IntheGeneraltab,maketheseschanges:1)changetheComponentInstanceNametoQ,2)changetheSymbolNametoSYM_BJT_NPNbyclickingthearrowandselectingit(thisisthebuiltinsymbol),3)inthe

Builtinsymbol:SYM_BJT_NPN

SOT23fixedartwork

• Lab 3: DC Simulations

Artworkfield,selectFixedandSOT23asshownhere.

c. ClickSaveAELFiletowritethesechangesbutdonotclosethisdialogyetbecauseyoustillneedtosetotherparameters.

e. Intheschematicwindow,Savethedesign(clicktheiconshownhere)tomakesureallyourworkcreatingthissubcircuitwillnotbelost.Inthenextsteps,youwillseehowtheDesignParameterswillbeused.

Theparameterbetaisnowrecognizedasavariableofthiscircuit.Itsvaluecannowbepassed(assigned)fromanupperlevelhierarchywhenyouusebjt_pkgasasubcircuit.

NOTES:multiplicity_M

Youcandefinemultiplecomponentsinparallel.Youcanalsocopyparametersfromanotherdeviceorfile.

• Lab 3: DC Simulations

2009

6. Useacurvetracertemplatetotestthebjt_pkgsubcircuit.

Thisiswhereyouwillconnectthedevice(bjt_pkg)inthenextfewsteps.

• Lab 3: DC Simulations

b. SavethedesignandthenclicktheComponentLibraryicon(shownhere).

c. Whenthedialogopens,selectProjects>Amp1900andthenclickanddragthebjt_pkgintotheschematicandinsertitasshownhere.Everycircuitthatyoubuildwillbeavailableintheprojectlibraryasasubcircuit.

• Lab 3: DC Simulations

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DCCurvesatbeta=100

7. ModifythetemplateParameterSweep.

a. ChangetheParameterSweepIBBvaluesto:0uAto100uAin10uAstepsasshownhere.DonotchangetheDCsimulationcontrollerdefaultsettingsforsweepingVCEtheyareOK.NoticethattheVAR1variables(VCE=0andIBB=0)donotrequiremodificationbecausetheyareonlyrequiredtoinitialize(declare)thevariableforthesimulator.

8. Simulateatbeta=100and160.

b. SimulateagainwithBeta=160bychangingchangingthevaluedirectlyontheschematic.Youshouldseetheupdatedvalues.

Parametersweepusedformultiplevariablesweeps.NotethatDC1isthename(SimInstanceName)ofthesimulationcontroller.

Onlyonevariablecanbesweptinthecontroller.

VarEqnisrequiredtoinitializevariables.

• Lab 3: DC Simulations

StartupandWorkingdirectoryicons:

HideandShowicons:

9. OpenanewdesignandviewtheprojectintheMainwindow

e. ClickontheFileViewandthenthetheProjectViewtabsnoticethatthethatthetoolbariconschange.

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

g. AlsotrytheHideandShowicons.

Datasetsareinthedatafolder,andschematicdesignsareinthenetworksfolder.

• Lab 3: DC Simulations

2009

• Lab 3: DC Simulations

10. Setupandsimulatethedcbiasparametersweep.

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

BUILDthecircuitwithoutatemplatethestepsfollow:

a. Insertthebjt_pkgusinglibraryiconorthecomponenthistory.Nowpushintothebjt_pkgandclickFile>DesignParameters.Resetthebetaparameterdefaultto160,popoutanddeletethebjt_pkgandreinsertitbetaisnow160wheneveryouusethemodeledcircuit.

• Lab 3: DC Simulations

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

g. InsertawirelabelVBEatthebase.Thevoltagesatthatnodewillappearinthedatasetforuseincalculatingbiasresistorvalues.

11. CalculatebiasvaluesRbandRcforagroundedemittercircuit.

b. SelecttheRbEqnandusethekeyboardCtrlCandCtrlVtocopy/pasteititwillbecomeRb1.

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

• Lab 3: DC Simulations

12. Setupthebiasednetwork.

Nowthatyouhavethecalculatedbiasresistorvalues,youcantestthebiasnetwork.

b. Modifythedesignasshown.BeginbydeletingthecurrentsourceIBB,theI_Probe,andtheVarEqn.

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

d. ChangetheinstanceRnamestoRCandRBasshown.

e. SettheV_DCsupply:Vdc=5V.Wirethecircuitandorganizeit.

f. DeletetheDCsimulationcontrollerandputanewoneinitsplacethisisfasterandmoreefficientthanremovingthesweepsettings.Becausethereisnosweep,youdonothavetosetanythingtocheckDCvalues.

InsertthecursorandtypeovertorenameittoRC.

• Lab 3: DC Simulations

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13. SimulateandannotatetheDCsolution.

NOTE:Nodenames(pin/wirelabels)suchasVCorVBEcanbemovedbydraggingthemwithyourcursor.

• Lab 3: DC Simulations

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

14. OPTIONAL:SweepComponentModelTemperatures

a. EdittheDCcontrollerselectitandclicktheediticon.

c. InsertVCandVBEnode/pinlabels.

NOTE:TheTriseparameter(temperatureriseoveroverambient)canbespecifiedonindividualcomponents.

• Lab 3: DC Simulations

2009

EXTRA EXERCISES:

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

2. ReplacetheGummelPoonmodelcardwithanothermodel(Mextram)andresimulate.Afterward,comparetheresults.

3. InsertthetemplateSP_NWA_TwhichgeneratesSparametersforabjtatallthespecifiedbiaspoints.Tryusingthiswithyourbjt_pkg.

• Lab 3: DC Simulations

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