Bipolar junction transistors

Bipolar Junction Transistors (BJTs)

General form

QXXXXXXX NC NB NE <NS> MNAME <AREA> <OFF> <IC=VBE, VCE> <TEMP=T>

Examples

Q23 10 24 13 QMOD IC=0.6, 5.0
Q50A 11 26 4 20 MOD1

NC, NB, and NE are the collector, base, and emitter nodes, respectively. NS is the (optional) substrate node. If unspecified, ground is used. MNAME is the model name, AREA is the area factor, and OFF indicates an (optional) initial condition on the device for the dc analysis. If the area factor is omitted, a value of 1.0 is assumed. The (optional) initial condition specification using IC=VBE, VCE is intended for use with the UIC option on the .TRAN control line, when a transient analysis is desired starting from other than the quiescent operating point. See the .IC control line description for a better way to set transient initial conditions. The (optional) TEMP value is the temperature at which this device is to operate, and overrides the temperature specification on the .OPTION control line.

Parameters: Bipolar junction transistor

BJT Models (NPN/PNP)

The bipolar junction transistor model in SPICE is an adaptation of the integral charge control model of Gummel and Poon. This modified Gummel-Poon model extends the original model to include several effects at high bias levels. The model automatically simplifies to the simpler Ebers-Moll model when certain parameters are not specified. The parameter names used in the modified Gummel-Poon model have been chosen to be more easily understood by the program user, and to reflect better both physical and circuit design thinking.

The dc model is defined by the parameters IS, BF, NF, ISE, IKF, and NE which determine the forward current gain characteristics, IS, BR, NR, ISC, IKR, and NC which determine the reverse current gain characteristics, and VAF and VAR which determine the output conductance for forward and reverse regions. Three ohmic resistances RB, RC, and RE are included, where RB can be high current dependent. Base charge storage is modeled by forward and reverse transit times, TF and TR, the forward transit time TF being bias dependent if desired, and nonlinear depletion layer capacitances which are determined by CJE, VJE, and MJE for the B-E junction , CJC, VJC, and MJC for the B-C junction and CJS, VJS, and MJS for the C-S (Collector-Substrate) junction. The temperature dependence of the saturation current, IS, is determined by the energy-gap, EG, and the saturation current temperature exponent, XTI. Additionally base current temperature dependence is modeled by the beta temperature exponent XTB in the new model. The values specified are assumed to have been measured at the temperature TNOM, which can be specified on the .OPTIONS control line or overridden by a specification on the .MODEL line.

The BJT parameters used in the modified Gummel-Poon model are listed below. The parameter names used in earlier versions of SPICE2 are still accepted.

Modified Gummel-Poon BJT Parameters.

name	parameter	units	default	example	area
IS	transport saturation current	A	1.0e-16	1.0e-15	*
BF	ideal maximum forward beta	-	100	100
NF	forward current emission coefficient	-	1.0	1
VAF	forward Early voltage	V	infinite	200
IKF	corner for forward beta high current roll-off	A	infinite	0.01	*
ISE	B-E leakage saturation current	A	0	1.0e-13	*
NE	B-E leakage emission coefficient	-	1.5	2
BR	ideal maximum reverse beta	-	1	0.1
NR	reverse current emission coefficient	-	1	1
VAR	reverse Early voltage	V	infinite	200
IKR	corner for reverse beta high current roll-off	A	infinite	0.01	*
ISC	B-C leakage saturation current	A	0	1.0e-13	*
NC	B-C leakage emission coefficient	-	2	1.5
RB	zero bias base resistance	Ω	0	100	*
IRB	current where base resistance falls halfway to its min value	A	infinite	0.1	*
RBM	minimum base resistance at high currents	Ω	RB	10	*
RE	emitter resistance	Ω	0	1	*
RC	collector resistance	Ω	0	10	*
CJE	B-E zero-bias depletion capacitance	F	0	2pF	*
VJE	B-E built-in potential	V	0.75	0.6
MJE	B-E junction exponential factor	-	0.33	0.33
TF	ideal forward transit time	sec	0	0.1ns
XTF	coefficient for bias dependence of TF	-	0
VTF	voltage describing VBC dependence of TF	V	infinite
ITF	high-current parameter for effect on TF	A	0		*
PTF	excess phase at freq=1.0/(TF*2PI) Hz	deg	0
CJC	B-C zero-bias depletion capacitance	F	0	2pF	*
VJC	B-C built-in potential	V	0.75	0.5
MJC	B-C junction exponential factor	-	0.33	0.5
XCJC	fraction of B-C depletion capacitance connected to internal base node	-	1
TR	ideal reverse transit time	sec	0	10ns
CJS	zero-bias collector-substrate capacitance	F	0	2pF	*
VJS	substrate junction built-in potential	V	0.75
MJS	substrate junction exponential factor	-	0	0.5
XTB	forward and reverse beta temperature exponent	-	0
EG	energy gap for temperature effect on IS	eV	1.11
XTI	temperature exponent for effect on IS	-	3
KF	flicker-noise coefficient	-	0
AF	flicker-noise exponent	-	1
FC	coefficient for forward-bias depletion capacitance formula	-	0.5
TNOM	Parameter measurement temperature	C	27	50

Parameters: Bipolar junction transistor