Q. Bipolar transistor

Symbol Names: NPN, PNP, NPN2, PNP2

Syntax: Qxxx Collector Base Emitter [Substrate Node]

+ model [area] [off] [IC=<Vbe, Vce>] [temp=<T>]

Example:

Q1 C B E MyNPNmodel

.model MyNPNmodel NPN(Bf=75)

Bipolar transistors require a model card to specify its characteristics. The model card keywords NPN and PNP indicate the polarity of the transistor.

The bipolar junction transistor model 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, quasi-saturation, and substrate conductivity. The model automatically simplifies to the Ebers-Moll model when certain parameters are not specified. 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 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.

Modified Gummel-Poon BJT Parameters

Name	Description	Units	Default
Is	Transport saturation current	A	1e-16
Bf	Ideal maximum forward beta	-	100
Nf	Forward current emission coefficient	-	1.
Vaf	Forward Early voltage	V	Infin.
Ikf	Corner for forward beta high current roll-off	A	Infin.
Ise	B-E leakage saturation current	A	0.
Ne	B-E leakage emission coefficient	-	1.5
Br	Ideal maximum reverse beta	-	1.
Nr	Reverse current emission coefficient	-	1.
Var	Reverse Early voltage	V	Infin.
Ikr	Corner for reverse beta high current roll-off	A	Infin.
Isc	B-C leakage saturation current	A	0
Nc	B-C leakage emission coefficient	-	2
Rb	Zero-bias base resistance	W	0
Irb	Current where base resistance falls halfway to its min value	A	Infin.
Rbm	Minimum base resistance at high currents	W	Rb
Re	Emitter resistance	W	0.
Rc	Collector resistance	W	0.
Cje	B-E zero-bias depletion capacitance	F	0.
Vje	B-E built-in potential	V	0.75
Mje	B-E junction exponential factor	-	0.33
Tf	Ideal forward transit time	sec	0.
Xtf	Coefficient for bias dependence of Tf	-	0.
Vtf	Voltage describing Vbc dependence of Tf	V	Infin.
Itf	High-current parameter for effect on Tf	A	0.
Ptf	Excess phase at freq=1/(Tf2PI)Hz	º	0.
Cjc	B-C zero-bias depletion capacitance	F	0.
Vjc	B-C built-in potential	V	0.75
Mjc	B-C junction exponential factor	-	0.33
Xcjc	Fraction of B-C depletion capacitance connected to internal base node	-	1.
Tr	Ideal reverse transit time	sec	0.
Cjs	Zero-bias collector-substrate capacitance	F	0.
Vjs	Substrate junction built-in potential	V	0.75
Mjs	Substrate junction exponential factor	-	0.
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	ºC	27
Cn	Quasi-saturation temperature coefficient for hole mobility	2.42 NPN 2.2 PNP
D	Quasi-saturation temperature coefficient for scattering-limited hole carrier velocity	.87 NPN .52 PNP
Gamma	Epitaxial region doping factor		1e-11
Qco	Epitaxial region charge factor	Coul	0.
Quasimod	Quasi-saturation flag for temperature dependence	-	(not set)
Rco	Epitaxial region resistance	W	0.
Vg	Quasi-saturation extrapolated bandgap voltage at 0ºK	V	1.206
Vo	Carrier mobility knee voltage	V	10.
Tre1	Re linear temperature coefficient	1/ºC	0.
Tre2	Re quadratic temperature coefficient	1/ºC²	0.
Trb1	Rb linear temperature coefficient	1/ºC	0.
Trb2	Rb quadratic temperature coefficient	1/ºC²	0.
Trc1	Rc linear temperature coefficient	1/ºC	0.
Trc2	Rc quadratic temperature coefficient	1/ºC²	0.
Trm1	Rmb linear temperature coefficient	1/ºC	0.
Trm2	Rmb quadratic temperature coefficient	1/ºC²	0.
Iss	Substrate junction saturation current	A	0.
Ns	Substrate junction emission Coefficient	-	1.

The model parameter "level" can be used to specify another type of BJT in LTspice. Due to a generous contribution of source code from Dr.-Ing. Dietmar Warning of DAnalyse GmbH, Berlin, Germany; LTspice includes a version of VBIC. Set

Level=9 to use the alternate device. Level 4 is a synonym for level 9. The following documentation has been supplied by Dr. Warning:

VBIC - Vertical Bipolar Inter Company model

The VBIC model is a extended development of the Standard Gummel-Poon (SGP) model with the focus of integrated bipolar transistors in today's modern semiconductor technologies. With the implemented modified Quasi-Saturation model from Kull and Nagel it is also possible to model the special output characteristic of switching transistors. It is a widely used alternative to the SGP model for silicon, SiGe and III-V HBT devices.

VBIC Capabilities compared to Standard Gummel-Poon Model

o Integrated Substrate transistor for parasitic devices in integrated processes

o Weak avalanche and Base-emitter breakdown model

o Improved Early Effect modeling

o Physical separation of Ic and Ib

o Improved Depletion capacitance model

o Improved temperature modeling

o Self-heating modeling (not in this version)

Model Structure

$image\vbic.gif$

Parameters

Because the VBIC model is based on SGP model it is possible to start with SGP parameters, carry out some transformations. Following parameters are from VBIC version 1.2, which is implemented in LTSpice in the 4-terminal version without excess phase network and self-heating effect. To switch from SGP to VBIC you should set the extra parameter level to 9.

Name	Parameter meaning	Unit	Default
tnom	Parameter measurement temperature	ºC	27.
rcx	Extrinsic coll resistance	W	0.1
rci	Intrinsic coll resistance	W	0.1
vo	Epi drift saturation voltage	V	Infin.
gamm	Epi doping parameter		0.0
hrcf	High current RC factor		Infin.
rbx	Extrinsic base resistance	W	0.1
rbi	Intrinsic base resistance	W	0.1
re	Intrinsic emitter resistance	W	0.1
rs	Intrinsic substrate resistance	W	0.1
rbp	Parasitic base resistance	W	0.1
is	Transport saturation current	A	1e-16
nf	Forward emission coefficient		1.
nr	Reverse emission coefficient		1.
fc	Fwd bias depletion capacitance limit		0.9
cbeo	Extrinsic B-E overlap capacitance	F	0.0
cje	Zero bias B-E depletion capacitance	F	0.0
pe	B-E built in potential	V	0.75
me	B-E junction grading coefficient		0.33
aje	B-E capacitance smoothing factor		-0.5
cbco	Extrinsic B-C overlap capacitance	F	0.
cjc	Zero bias B-C depletion capacitance	F	0.
qco	Epi charge parameter	C	0.
cjep	B-C extrinsic zero bias capacitance	F	0.
pc	B-C built in potential	V	0.75
mc	B-C junction grading coefficient		0.33
ajc	B-C capacitance smoothing factor		-0.5
cjcp	Zero bias S-C capacitance	F	0.
ps	S-C junction built in potential	V	0.75
ms	S-C junction grading coefficient		0.33
ajs	S-C capacitance smoothing factor		-0.5
ibei	Ideal B-E saturation current	A	1e-18
wbe	Portion of IBEI from Vbei 1-WBE from Vbex		1.
nei	Ideal B-E emission coefficient		1.
iben	Non-ideal B-E saturation current	A	0.
nen	Non-ideal B-E emission coefficient		2.
ibci	Ideal B-C saturation current	A	1e-16
nci	Ideal B-C emission coefficient		1.
ibcn	Non-ideal B-C saturation current	A	0.
ncn	Non-ideal B-C emission coefficient		1.
avc1	B-C weak avalanche parameter 1	1/V	0.
avc2	B-C weak avalanche parameter 2	1/V	0.
isp	Parasitic transport saturation current	A	0.
wsp	Portion of ICCP		1.
nfp	Parasitic fwd emission coefficient		1.
ibeip	Ideal parasitic B-E saturation current	A	0.
ibenp	Non-ideal parasitic B-E saturation current	A	0.
ibcip	Ideal parasitic B-C saturation current	A	0.
ncip	Ideal parasitic B-C emission coefficient		1.
ibcnp	Non-ideal parasitic B-C saturation current	A	0.
ncnp	Non-ideal parasitic B-C emission coefficient		2.
vef	Forward Early voltage		Infin.
ver	Reverse Early voltage		Infin.
ikf	Forward knee current	A	Infin.
ikr	Reverse knee current	A	Infin.
ikp	Parasitic knee current	A	Infin.
tf	Ideal forward transit time	s	0.
qtf	Variation of TF with base-width modulation		0.
xtf	Coefficient for bias dependence of TF		0.
vtf	Voltage giving VBC dependence of TF	V	Infin.
itf	High current dependence of TF	A	Infin.
tr	Ideal reverse transit time	sec	0.
td	Forward excess-phase delay time	Sec	0.
kfn	B-E Flicker Noise Coefficient		0.
afn	B-E Flicker Noise Exponent		1.
bfn	B-E Flicker Noise 1/f dependence		1.0
xre	Temperature exponent of RE		0.
xrbi	Temperature exponent of RBI		0.
xrci	Temperature exponent of RCI		0.
xrs	Temperature exponent of RS		0.
xvo	Temperature exponent of VO		0.
ea	Activation energy for IS	V	1.12
eaie	Activation energy for IBEI	V	1.12
eaic	Activation energy for IBCI/IBEIP	V	1.12
eais	Activation energy for IBCIP	V	1.12
eane	Activation energy for IBEN	V	1.12
eanc	Activation energy for IBCN/IBENP	V	1.12
eans	Activation energy for IBCNP	V	1.12
xis	Temperature exponent of IS		3.
xii	Temperature exponent of IBEI,IBCI,IBEIP,IBCIP		3.
xin	Temperature exponent of IBEN,IBCN,IBENP,IBCNP		3.
tnf	Temperature exponent of NF		0.
tavc	Temperature exponent of AVC2		0.
rth	Thermal resistance	K/W	0.
cth	Thermal capacitance	Ws/K	0.
vrt	Punch-through voltage of internal B-C junction	V	0.
art	Smoothing parameter for reach-through		0.1
ccso	Fixed C-S capacitance	F	0.
qbm	Select SGP qb formulation		0.
nkf	High current beta rolloff		0.5
xikf	Temperature exponent of IKF		0.
xrcx	Temperature exponent of RCX		0.
xrbx	Temperature exponent of RBX		0.
xrbp	Temperature exponent of RBP		0.
isrr	Separate IS for fwd and rev		1.
xisr	Temperature exponent of ISR		0.
dear	Delta activation energy for ISRR		0.
eap	Excitation energy for ISP		1.12
vbbe	B-E breakdown voltage	V	0.
nbbe	B-E breakdown emission coefficient		1.
ibbe	B-E breakdown current		1e-06
tvbbe1	Linear temperature coefficient of VBBE		0.
tvbbe2	Quadratic temperature coefficient of VBBE		0.
tnbbe	Temperature coefficient of NBBE		0.
ebbe	exp(-VBBE/(NBBE*Vtv))		0.
dtemp	Locale Temperature difference	º	0.
vers	Revision Version		1.2
vref	Reference Version		0.

References:

C. C. McAndrew et al., "Vertical Bipolar Inter Company 1995: An Improved Vertical, IC Bipolar Transistor Model", Proceedings of the IEEE Bipolar Circuits and Technology Meeting, pp. 170 − 177, 1995

C. C. McAndrew et.al., VBIC95, "The Vertical Bipolar Inter-Company Model", IEEE Journal of Solid State Circuits, vol. 31, No. 10, October 1996

C. C. McAndrew, VBIC Model Definition, Release 1.2, 18. Sep. 1999