3.17  Q: Bipolar Junction Transistor

3.17.1  Syntax

Device

Qxxxxxxx nc nb ne ns mname {area} {args}
.BJT label nc nb ne ns mname {area} {args}

Model (required)

.model mname NPN {args}
.model mname PNP {args}

3.17.2  Purpose

Bipolar junction transistor,

3.17.3  Comments

Nc, nb, ne, and ns are the collector, base, emitter, and substrate nodes, respectively. Mname is the model name. The substrate node is optional.

Area is a unit-less multiplier for the area.

The options (.options command) rstray determines whether or not series resistances are included. rstray is the default. Norstray is the equivalent of setting the model parameters rc, re, and rb all to zero.

Entering a parameter value of 0 is not the same as not specifying it. This behavior is not compatible with SPICE. In SPICE, a value of 0 is often interpreted as not specified, with the result being to calculate it some other way. If you want it to be calculated, don't specify it.

Another subtle difference from SPICE is that Gnucap may omit some unnecessary parts of the model, which may affect some reported values. It should not affect any voltages or currents.

3.17.4  Element Parameters

Basic Spice compatible parameters

M = x
Device multiplier. (Default = 1.) Equivalent number of devices in parallel.

AREA = x
Junction area. (Default = 1) This is a scaling parameter, with no relevant actual units.

OFF
(Default = not specified) If this word is specified, the initial guess will assume the device is off.

TEMP = x
Junction temperature. (Default = the global temperature.)

ICVBE = x
Initial condition, Vbe. (Default = NA) Use this as the initial condition, when the UIC option is specified. The syntax is different from Spice, but the function is the same.

ICVCE = x
Initial condition, Vce. (Default = NA) Use this as the initial condition, when the UIC option is specified. The syntax is different from Spice, but the function is the same.

3.17.5  Model Parameters

Basic DC parameters

BF = x
Ideal maximum forward beta. (Default = 100) Alternate name is BFM.

BR = x
Ideal maximum reverse beta. (Default = 1) Alternate name is BRM.

IBC = x
BC Transport saturation Current per area. (Default = IS) If omitted, IS is used. You should specify either IS or IBC, not both.

IBE = x
BE Transport saturation Current per area. (Default = IS) If omitted, IS is used. You should specify either IS or IBE, not both.

IS = x
Transport saturation Current per area. (Default = 1e-16) If IBE and IBC are specified, they are used instead. Do not specify both.

NF = x
Forward current emission coefficient. (Default = 1)

NR = x
Reverse current emission coefficient. (Default = 1)

Base width modulation

VAF = x
Forward Early voltage. (Default = Infinite) Alternate names are VA and VBF.

VAR = x
Reverse Early voltage. (Default = Infinite) Alternate name is VB.

Low current beta degeneration

ISC = x
B-C leakage saturation current. (Default = c4 * is)

C4 = x
B-C leakage scale factor. (Default = 0) Alternate name is JLC.

NC = x
B-C leakage emission coefficient. (Default = 2)

ISE = x
B-E leakage saturation current. (Default = c2 * is)

C2 = x
B-E leakage scale factor. (Default = 0) Alternate name is JLE.

NE = x
B-E leakage emission coefficient. (Default = 1.5)

High current beta degeneration

IKF = x
Forward beta roll-off corner current. (Default = Infinite) Alternate names are JBF and IK.

IKR = x
Reverse beta roll-off corner current. (Default = Infinite) Alternate name is JBR.

Parasitic resistance

IRB = x
Current for base resistance=(rb+rbm)/2". (Default = Infinite) Current where base resistance falls halfway to its minimum value. Alternate name is JRB.

RB = x
Zero bias base resistance. (Default = 0)

RBM = x
Minimum base resistance at high current. (Default = rb)

RE = x
Emitter resistance. (Default = 0)

RC = x
Collector resistance. (Default = 0)

Junction capacitance

CJC = x
Zero bias B-C depletion capacitance. (Default = 0)

CJE = x
Zero bias B-E depletion capacitance. (Default = 0)

CJS = x
Zero bias C-S capacitance. (Default = 0) Alternate name is CCS.

FC = x
Coefficient for forward-bias depletion capacitance formula. (Default = .5)

MJC = x
B-C junction grading coefficient. (Default = .33) Alternate names are MJ and MC.

MJE = x
B-E junction grading coefficient. (Default = .33) Alternate name is ME.

MJS = x
Substrate junction grading coefficient. (Default = 0) Alternate names are MS and MSUB.

VJC = x
B-C built in potential. (Default = .75) Alternate name is PC.

VJE = x
B-E built in potential. (Default = .75) Alternate name is PE.

VJS = x
Substrate junction built in potential. (Default = .75) Alternate name is PS.

XCJC = x
Fraction of B-C capacitance connected to internal base node. (Default = 1)

Parasitic capacitance

CBCP = x
External B-C constant parasitic capacitance. (Default = 0)

CBEP = x
External B-E constant parasitic capacitance. (Default = 0)

CBSP = x
External B-S constant parasitic capacitance for lateral transistors. (Default = 0)

CCSP = x
External B-C constant parasitic capacitance for vertical transistors. (Default = 0)

Transit time

ITF = x
High current dependence of TF. (Default = 0)

PTF = x
Excess phase at freq=1.0/(TF*2PI) Hz. (Default = 0)

TF = x
Ideal forward transit time. (Default = 0)

TR = x
Ideal reverse transit time. (Default = 0)

VTF = x
Voltage giving VBC dependence of TF. (Default = Infinite)

XTF = x
Coefficient for bias dependence of TF. (Default = 0)

Temperature effects

XTB = x
Forward and reverse beta temperature exponent. (Default = 0)

XTI = x
Temperature exponent for effect on IS. (Default = 3)

EG = x
Energy gap for IS temperature dependency. (Default = 1.11)

TNOM = x
Parameter measurement temperature, Celsius. (Default = 27)

3.17.6  Probes

This is not a complete list. All “calculated parameters” can be probed. See the source file d_bjt.model for a list.

All parameters of the internal elements (Ice, Ipi, Imu, Cbx, Cbc, Ccs, Cbe, Rc, Re, Yb, Cbcp, Cbep, Cbs) are available. To access them, concatenate the labels for the internal element with this device, separated by a dot. Cbe.Q6 is the base to emitter capacitance of Q6.

There are no probes available in AC analysis except for the internal elements.
VBEINT
Base-emitter internal voltage.

VBCINT
Base-collector internal voltage.

VBXINT
External base to internal base voltage.

VCSINT
Collector-substrate internal voltage.

VBS
Base-substrate voltage.

VBE
Base-emitter voltage.

VBC
Base-collector voltage.

VCS
Collector-substrate voltage.

VCB
Collector-base voltage.

VCE
Collector-emitter voltage.

VES
Emitter-substrate voltage.

VEB
Emitter-base voltage.

VEC
Emitter-collector voltage.

VB
Base-ground voltage.

VC
Collector-ground voltage.

VE
Emitter-ground voltage.

VS
Substrate-ground voltage.

VBI
Internal Base-ground voltage.

VCI
Internal Collector-ground voltage.

VEI
Internal Emitter-ground voltage.

ICE
Collector-emitter current.

ICEOffset
Offset part of ICE.

GO
Output (collector-emitter) conductance.

GM
Transconductance.

IPI
Base-emitter current.

IPIOffset
Offset part of IPI.

GPI
Base-emitter conductance.

IMU
Base-collector current.

IMUOffset
Offset part of IMU.

GMU
Base-collector conductance.

IB
Base current.

GX
Conductance of base spreading resistance.

RX
Base spreading resistance.

IC
Collector current.

IE
Emitter current.

QBX
External Base-collector charge.

CQBX
External Base-collector capacitance.

CBX
External Base-collector capacitance (CQBX).

QBC
Internal Base-collector charge.

CQBC
Internal Base-collector capacitance.

CBC
Internal Base-collector capacitance (CQBC).

CMU
Internal Base-collector capacitance (CQBC).

QCS
Collector-substrate charge.

CQCS
Collector-substrate capacitance.

CCS
Collector-substrate capacitance (CQCS).

QBE
Base-emitter charge.

CQBE
Base-emitter capacitance.

CBE
Base-emitter capacitance. (CQBE).

CPI
Base-emitter capacitance. (CQBE).

P
Power.

PD
Power dissipated. The power dissipated as heat. It is always positive and does not include power sourced. It should be the same as P because transistors cannot generate energy.

PS
Power sourced. The power sourced by the part. It is always positive and does not consider its own dissipation. It should be 0 because transistors cannot generate energy.
All parameters of the internal elements (Ice, Ipi, Imu, Rc, Re, Yb, Cbx, Cbc, Ccs, Cbe, Cbcp, Cbep, Cbsp, Ccsp) are available. To access them, concatenate the labels for the internal element with this device, separated by a dot. Cbe.Q6 is the base to emitter capacitance of Q6.

In this release, there are no probes available in AC analysis except for the internal elements.