(Q) BJT Statement

The standard SPICE bipolar junction transistor (BJT) model based on the Gummel-Poon equations is supported [1] [2]. We have made minor improvements to the PN-junction currents in reverse bias to ensure continuity of the modeling equations. The excess phase of the forward current is modeled using a companion model [3].

Recommended

Qname collector base emitter <substrate> modelName <<AREA>=area> <IC=vbe,vce> <TEMP=temp> <M=m>
.MODEL modelName NPN <NAME=value ...>

Legacy

Qname collector base emitter <substrate> modelName <<AREA>=area> <off> <IC=vbe,vce> <TEMP=temp> <M=m>
.MODEL modelName NPN <NAME=value ...>

By default, an initial guess of \(V_{\text{be}} = 0.6\,\text{V}\) (\(-0.6\,\text{V}\)) is used in the operating point analysis for a NPN-type (PNP-type) bipolar junction transistor. When the off flag is set, an initial guess of zero is used instead. Note that this option does not enforce a constraint on the solution found during the operating point analysis.

• The substrate node is optional and connected to ground unless specified.

• The BJT device type NPN or PNP must be specified in the model statement.

• You can customize this model by providing a list of model parameter (name-value format) at the end of the .MODEL statement.

• When importing a BJT model, the substrate node will be omitted.

Instance Parameters

Parameter	Description	Default Value
AREA	Device area (number of parallel devices)	\(1\)
IC	Initial condition voltages (\(V_{\text{be}}, V_{\text{ce}}\)).	none
TEMP	Device temperature	\(27\,^\circ\text{C}\)
M	Number of parallel devices	\(1\)

• When the IC parameter is given, initial values for both the base-emitter (\(V_{\text{be}}\)) and the collector-emitter voltage (\(V_{\text{ce}}\)) must be specified.

Model Parameters

Parameter	Description	Default Value
T_ABS	Device temperature	\(27\,^\circ\text{C}\)
TNOM	Nominal temperature	\(27\,^\circ\text{C}\)
IS	Reverse saturation current	\(10^{-16}\,\text{A}\)
XTI	Temperature exponent for IS	\(3\)
EG	Band gap energy	\(1.11\,\text{eV}\)
NF	Emission coefficient for the forward current	\(1\)
NR	Emission coefficient for the reverse current	\(1\)
BF	Ideal forward current gain	\(100\)
BR	Ideal reverse current gain	\(1\)
XTB	Temperature exponent for BF and BR	\(0\)
VAF / VA	Forward Early voltage	\(+\infty\,\text{V}\)
VAR / VB	Reverse Early voltage	\(+\infty\,\text{V}\)
IKF	Roll-off corner current for the forward current gain	\(+\infty\,\text{A}\)
IKR	Roll-off corner current for the reverse current gain	\(+\infty\,\text{A}\)
ISC	Reverse saturation current for the base-collector leakage junction	\(0\,\text{A}\)
ISE	Reverse saturation current for the base-emitter leakage junction	\(0\,\text{A}\)
NC	Emission coefficient for the base-collector leakage junction	\(2\)
NE	Emission coefficient for the base-emitter leakage junction	\(1.5\)
VJC	Base-collector junction potential	\(0.75\,\text{V}\)
MJC	Base-collector junction grading coefficient	\(0.33\)
CJC	Base-collector zero-bias junction capacitance	\(0\,\text{F}\)
XCJC	Fraction of the base-collector capacitance connected to the internal base node	\(1\)
VJE	Base-emitter junction potential	\(0.75\,\text{V}\)
MJE	Base-emitter junction grading coefficient	\(0.33\)
CJE	Base-emitter zero-bias junction capacitance	\(0\,\text{F}\)
VJS	Substrate-collector junction potential	\(0.75\,\text{V}\)
MJS	Substrate-collector junction grading coefficient	\(0\)
CJS	Substrate-collector zero-bias junction capacitance	\(0\,\text{F}\)
FC	Forward-bias depletion capacitance coefficient	\(0.5\)
TR	Reverse transit time	\(0\,\text{s}\)
TF	Forward transit time	\(0\,\text{s}\)
VTF	Voltage giving the base-collector voltage dependence of the forward transit time.	\(+\infty\,\text{V}\)
ITF	Forward transit time fall-off current	\(0\,\text{A}\)
XTF	Forward transit time bias dependence coefficient	\(1\)
PTF	Excess phase	\(0^\circ\)
RC	Collector resistance	\(0\,\Omega\)
RE	Emitter resistance	\(0\,\Omega\)
RB	Zero-bias base resistance	\(0\,\Omega\)
RBM	Minimum base resistance at high current	RB
IRB	Current when the base resistance drops to (RB + RBM)/2	\(+\infty\,\text{A}\)
TRC1	Temperature coefficient for RC (first order correction)	\(0\,^\circ\text{C}^{-1}\)
TRC2	Temperature coefficient for RC (second order correction)	\(0\,^\circ\text{C}^{-2}\)
TRB1	Temperature coefficient for RB (first order correction)	\(0\,^\circ\text{C}^{-1}\)
TRB2	Temperature coefficient for RB (second order correction)	\(0\,^\circ\text{C}^{-2}\)
TRE1	Temperature coefficient for RE (first order correction)	\(0\,^\circ\text{C}^{-1}\)
TRE2	Temperature coefficient for RE (second order correction)	\(0\,^\circ\text{C}^{-2}\)
TRM1	Temperature coefficient for RBM (first order correction)	\(0\,^\circ\text{C}^{-1}\)
TRM2	Temperature coefficient for RBM (second order correction)	\(0\,^\circ\text{C}^{-2}\)

• The instance parameter TEMP overwrites the model parameter T_ABS.

• The parameters representing currents and capacitances (starting with I and C) are multiplied by the AREA parameter.

• The parameters representing resistances (starting with R) are divided by the AREA parameter.

Note

• For the parameters VAF, VAR, VTF, IKF, IKR, and IRB, a value of \(0\) is interpreted as \(+\infty\).

• Some parameters encountered in semiconductor models are provided as additional information and do not affect the simulation. PLECS Spice ignores the following parameters: mfg, BVceo, Vceo, Ic, Icrating.

Examples

Q1 collector base emitter npnModel
.MODEL npnModel NPN IS=1e-14 BF=50 VAF=100 IKF=1
+ TF=10n TR=100n CJE=100p CJC=50p RC=1 RE=0.5 RB=5

References

[1]

H. K. Gummel and H. C. Poon, “An integral charge control model of bipolar transistors,” Bell System Technical Journal, vol. 49, no. 5, pp. 827-852, May-June 1970

[2]

P. Antognetti and G. Massobrio, “Semiconductor Device Modeling with Spice”, 2nd ed., McGraw-Hill, Inc., USA, 1993.

[3]

VBIC - Vertical Bipolar Intercompany Model, https://designers-guide.org/vbic/