Chapter 14 BJT Models - Class Home Pages - UWECE

1 : 1 Thu Jul 23 19:10:43 1998 Star-Hspice Manual, Release 14 BJT ModelsIThe bipolar-junction transistor (BJT) model in HSPICE is an adaptation of theintegral charge control model of Gummel and HSPICE model extends the original Gummel-Poon model to include severaleffects at high bias levels. This model automatically simplifies to the Ebers-Mollmodel when certain parameters (VAF, VAR, IKF, and IKR) are not Chapter covers the following topics:nUsing the BJT ModelnUsing the BJT ElementnUnderstanding the BJT Model StatementnUsing the BJT Models (NPN and PNP)nUnderstanding BJT CapacitancesnModeling Various Types of NoisenUsing the BJT Quasi-Saturation ModelnUsing Temperature Compensation EquationsnConverting National Semiconductor : 2 Thu Jul 23 19:10:43 1998 Using the BJT ModelBJT Models14-2 Star-Hspice Manual, Release the BJT ModelThe BJT model is used to develop BiCMOS, TTL, and ECL circuits.

2 ForBiCMOS devices, use the high current Beta degradation parameters, IKF andIKR, to modify high injection effects. The model parameter SUBS facilitates themodeling of both vertical and lateral geometrics. Model SelectionTo select a BJT device, use a BJT element and model statement. The elementstatement references the model statement by the reference model name. Thereference name is given as MOD1 in the following example. In this case an NPNmodel type is used to describe an NPN 3 2 5 MOD1 <parameters>.MODEL MOD1 NPN <parameters>Parameters can be specified in both element and model statements. The elementparameter always overrides the model parameter when a parameter is specifiedas both. The model statement specifies the type of BJT, for example, NPN : 3 Thu Jul 23 19:10:43 1998 BJT ModelsUsing the BJT ModelStar-Hspice Manual, Release OptionsControl options affecting the BJT model are: DCAP, GRAMP, GMIN, andGMINDC.

3 DCAP selects the equation which determines the BJT , GMIN, and GMINDC place a conductance in parallel with both thebase-emitter and base-collector pn junctions. DCCAP invokes capacitancecalculations in DC global depletion capacitance equation selection that uses the .OPTIONDCAP=<val> statement in a BJT model by including DCAP=<val> in theBJT s .MODEL a base, collector, and emitter resistance to the BJT model improves itsconvergence. The resistors limit the current in the device so that the forward-biased pn junctions are not 14-1: BJT OptionscapacitanceDCAP, DCCAP conductanceGMIN, GMINDC, : 4 Thu Jul 23 19:10:43 1998 Using the BJT ElementBJT Models14-4 Star-Hspice Manual, Release the BJT ElementThe BJT element parameters specify the connectivity of the BJT, normalizedgeometric specifications, initialization, and temperature formQxxx nc nb ne <ns> mname <aval> <OFF> <IC=vbeval,vceval> <M=val> <DTEMP=val>orQxxx nc nb ne <ns> mname <AREA=val> <AREAB=val> <AREAC=val> <OFF> <VBE=val> + <VCE=val> <M=val> <DTEMP=val>Table 14-2: BJT Element ParametersTypeParametersnetlistQxxx, mname, nb, nc, ne, nsgeometricAREA, AREAB, AREAC, MinitializationIC (VBE, VCE), OFFtemperatureDTEMPQxxxBJT element name.

4 Must begin with a Q , which can befollowed by up to 15 alphanumeric terminal node namenbbase terminal node nameneemitter terminal node namenssubstrate terminal node name, optional. Can be set in themodel with BULK= Node name referenceavalvalue for : 5 Thu Jul 23 19:10:43 1998 BJT ModelsUsing the BJT ElementStar-Hspice Manual, Release CX BX EX QPNP AREA= AREAB= AREAC= 10 24 13 QMOD IC= , 11 265 4 20 MOD1 ScalingScaling is controlled by the element parameters AREA, AREAB, AREAC, andM. The AREA parameter, the normalized emitter area, divides all resistors andmultiplies all currents and capacitors. AREAB and AREAC scale the size of thebase area and collector area. Either AREAB or AREAC is used for scaling,depending on whether vertical or lateral geometry is selected (using the SUBS model parameter). For vertical geometry, AREAB is the scaling factor for IBC,ISC, and CJC.

5 For lateral geometry, AREAC is the scaling factor. The scalingfactor is AREA for all other initial condition to OFF for this element in DC ,initial internal base to emitter voltage (vbeval) or initial internalcollector tovcevalemitter voltage (vceval). Overridden by the .IC factor to simulate multiple BJTs. All currents,capacitances, and resistances are affected by difference between element and circuit temperature(default= )AREA emitter area multiplying factor that affects resistors,capacitors, and currents (default= )AREAB base area multiplying factor that affects resistors, capacitors,and currents (default=AREA)AREAC collector area multiplying factor that affects resistors,capacitors, and currents (default=AREA) : 6 Thu Jul 23 19:10:43 1998 Using the BJT ElementBJT Models14-6 Star-Hspice Manual, Release scaling of the DC model parameters (IBE, IS, ISE, IKF, IKR, and IRB) forboth vertical and lateral BJT transistors, is determined by the following formula.

6 Where I is either IBE, IS, ISE, IKF, IKR, or both the vertical and lateral the resistor model parameters, RB, RBM, RE,and RC are scaled by the following R is either RB, RBM, RE, or RC. BJT Current ConventionThe direction of current flow through the BJT is assumed for example purposesin Figure 13-1. Use either I(Q1) or I1(Q1) syntax to print the collector (Q1) refers to the base current, I3(Q1) refers to the emitter current, and I4(Q1)refers to the substrate 13-1 BJT Current ConventionIeffAREA M I =ReffRAREA M -------------------------=nc(collector node)I1(Q1)ns(substrate node)I4(Q1)ne(emitter node)I3(Q1)nb(base node)I2(Q1) : 7 Thu Jul 23 19:10:43 1998 BJT ModelsUsing the BJT ElementStar-Hspice Manual, Release BJT Equivalent CircuitsHSPICE uses four equivalent circuits in the analysis of BJTs: DC, transient, AC,and AC noise circuits.

7 The components of these circuits form the basis for allelement and model equations. Since these circuits represent the entire BJT inHSPICE, every effort has been made to demonstrate the relationship between theequivalent circuit and the element/model fundamental components in the equivalent circuit are the base current (ib)and the collector current (ic). For noise and AC analyses, the actual ib and iccurrents are not used. The partial derivatives of ib and ic with respect to theterminal voltages vbe and vbc are used instead. The names for these partialderivatives are:Reverse Base ConductanceForward Base ConductanceCollector Conductanceg ib vbc ib vbe vce vbc ------------ : 8 Thu Jul 23 19:10:43 1998 Using the BJT ElementBJT Models14-8 Star-Hspice Manual, Release ib and ic equations account for all DC effects of the 13-1: Lateral Transistor, BJT Transient Analysisgmic vbe ------------vcecons==ic vbe ------------ic vbc ------------+=ic vbe ------------go = : 9 Thu Jul 23 19:10:43 1998 BJT ModelsUsing the BJT ElementStar-Hspice Manual, Release 13-2: Vertical Transistor, BJT Transient : 10 Thu Jul 23 19:10:43 1998 Using the BJT ElementBJT Models14-10 Star-Hspice Manual, Release 13-3: Lateral Transistor, BJT AC AnalysisCBCPCCSPCBEPB asecbcxrbcbcgbcrcCollectorgm : 11 Thu Jul 23 19:10.

8 43 1998 BJT ModelsUsing the BJT ElementStar-Hspice Manual, Release 13-4: Vertical Transistor, BJT AC AnalysisCBCPCBEPB asecbcxrbcbcgbcrcCollectorgm : 12 Thu Jul 23 19:10:43 1998 Using the BJT ElementBJT Models14-12 Star-Hspice Manual, Release 13-5: Lateral Transistor, BJT AC Noise AnalysisCBCPCCSPCBEPB asecbcxrbcbcgbcrcCollectorgm vbegoEmittercbe : 13 Thu Jul 23 19:10:43 1998 BJT ModelsUsing the BJT ElementStar-Hspice Manual, Release 13-6: Vertical Transistor, BJT AC Noise AnalysisTable 13-2: Equation Variable NamesVariableDefinitionscbcinternal base to collector capacitancecbcxexternal base to collector capacitancecbeinternal base to emitter capacitancecscsubstrate to collector capacitance (vertical transistor only)cbsbase to substrate capacitance (lateral transistor only)ffrequencygbcreverse base conductanceCBCPCBEPB asecbcxrbcbcgbcrcCollectorgm vbegoEmittercbe : 14 Thu Jul 23 19:10.

9 43 1998 Using the BJT ElementBJT Models14-14 Star-Hspice Manual, Release base conductancegmtransconductancegscsubstrat e to collector conductance (vertical transistor only)gocollector conductancegbsbase to substrate conductance (lateral transistor only)ibexternal base terminal currentibcDC current base to collectoribeDC current base to emittericexternal collector terminal currenticeDC current collector to emitterinbbase current equivalent noiseinccollector current equivalent noiseinrbbase resistor current equivalent noiseinrccollector resistor equivalent noiseinreemitter resistor current equivalent noiseibsDC current base to substrate (lateral transistor only)iscDC current substrate to collector (vertical transistor only)qbnormalized base chargerbbase resistancerbbshort-circuit base resistancevbsinternal base substrate voltagevscinternal substrate collector voltageTable 13-2: Equation Variable : 15 Thu Jul 23 19:10:43 1998 BJT ModelsUsing the BJT ElementStar-Hspice Manual, Release 13-3: Equation (Boltzmann s constant) (electron charge)ttemperature in Kelvin tt - tnomtnomtnom = + TNOM in Kelvinvt(t)k t/qvt(tmon)k : 16 Thu Jul 23 19:10:43 1998 Understanding the BJT Model StatementBJT Models14-16 Star-Hspice Manual, Release the BJT Model StatementGeneral mname NPN <(> <pname1 = val1>.)

10 <)> mname PNP <pname1 = val1> ..mnamemodel name. Elements refer to the model by this an NPN transistor modelpname1 Each BJT model can include several model a PNP transistor t2n2222a NPN+ ISS= 0. XTF= 1. NS = + CJS= 0. VJS= PTF= 0.+ MJS= 0. EG = AF = 1.+ ITF= VTF= F = + BR = IS = VAF= + VAR= IKF= IS = + NE = IKR= ISC= + NC = IRB= NF = + NR = RBM= RB = + RC = RE = MJE= + MJC= VJE= VJC= + TF = TR = CJE= + CJC= FC = XCJC= : 17 Thu Jul 23 19:10:43 1998 BJT ModelsUnderstanding the BJT Model StatementStar-Hspice Manual, Release BJT Basic Model ParametersTo permit the use of model parameters from earlier versions of HSPICE, manyof the model parameters have aliases, which are included in the model parameterlist in BJT Basic DC Model Parameters on page 14-19.