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

NameDescriptionUnitsDefault
IsTransport saturation currentA1e-16
IbcBase-collector saturation currentAIs
IbeBase-emitter saturation currentAIs
BfIdeal maximum forward beta-100
NfForward current emission coefficient-1.
VafForward Early voltageVInfin.
IkfCorner for forward beta high current roll-offAInfin.
nkHigh current roll-off coefficient-.5
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 Ω 0
Irb Current where base resistance falls halfway to its min value A Infin.
Rbm Minimum base resistance at high currents Ω Rb
Re Emitter resistance Ω 0.
Rc Collector resistance Ω 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/(Tf*2*Ω)Hz ° 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.
Xcjc2 Fraction of B-C depletion capacitance connected between internal base node and extrinsic collector - 0
extsub Extrinsicness of more intrinsic collector node used for substrate capacitance charge division - 0
Tr Ideal reverse transit time sec 0.
Cjs Zero-bias collector-substrate capacitance F 0.
Xcjs Fraction of Cjs connected internally to Rc 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
subs Geometry selector if LPNP is not used: 1 means vertical 2 means lateral - NPN: 1
PNP: 2
BVcbo Collector-base breakdown voltage - Infin.
nBVcbo Collector-base breakdown voltage coefficient - 5
BVbe Base-emitter breakdown voltage V Infin.
Ibvbe Current at base-emitter breakdown voltage A 1e-10
nbvbe Base-emitter breakdown coefficient - 1.
Tnom Parameter measurement temperature °C 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 Ω 0.
Vg Quasi-saturation extrapolated bandgap voltage at 0°K V 1.206
Vo Carrier mobility knee voltage V 10.
Tre1 Re linear temperature coefficient 1/°C 0.
Tre2 Re quadratic temperature coefficient 1/°C2 0.
Trb1 Rb linear temperature coefficient 1/°C 0.
Trb2 Rb quadratic temperature coefficient 1/°C2 0.
Trc1 Rc linear temperature coefficient 1/°C 0.
Trc2 Rc quadratic temperature coefficient 1/°C2 0.
Trm1 Rmb linear temperature coefficient 1/°C 0.
Trm2 Rmb quadratic temperature coefficient 1/°C2 0.
Iss Substrate junction saturation current A 0.
Ns Substrate junction emission Coefficient - 1.
Tvaf1 Vaf linear temperature coefficient 1/°C 0.
Tvaf2 Vaf quadratic temperature coefficient 1/°C2 0.
Tvar1 Var linear temperature coefficient 1/°C 0.
Tvar2 Var quadratic temperature coefficient 1/°C2 0.
Tikf1 Ikf linear temperature coefficient 1/°C 0.
Tikf2 Ikf quadratic temperature coefficient 1/°C2 0.
Trbm1 Rbm linear temperature coefficient 1/°C 0.
Trbm2 Rbm quadratic temperature coefficient 1/°C2 0.
Tbvcbo1 BVcbo linear temperature coefficient 1/°C 0.
Tbvcbo2 BVcbo quadratic temperature coefficient 1/°C2 0.

It is possible to annotate a model with device ratings. This information is displayed in the schematic capture GUI to assist in selecting a device but does not directly impact the electrical behavior in simulation. The following parameters may be specified.

NameDescriptionUnits
VceoMaximum collector-emitter voltage with the base floatingV
IcratingMaximum collector currentA
mfgName of manufacturer-

The model parameter "level" can be used to specify another type of BJT in LTspice.

Set Level=504 to use the MEXTRAM 504 transistor due to NXP(Philips).

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

Model Structure

VBIC 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 Description Unit Default
Tnom Parameter measurement temperature °C 27.
Rcx Extrinsic collector resistance Ω 0.1
Rci Intrinsic collector resistance Ω 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 Ω 0.1
Rbi Intrinsic base resistance Ω 0.1
Re Intrinsic emitter resistance Ω 0.1
Rs Intrinsic substrate resistance Ω 0.1
Rbp Parasitic base resistance Ω 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 Local Temperature difference ° 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