Z. MESFET and IGBT Transistors

Symbol Names: MESFET, NIGBT, PIGBT

Syntax: Zxxx D G S model [area] [m=<value>] [off] [IC=<Vds, Vgs>] [temp=<value>]

A MESFET transistor requires a model card to specify its characteristics. The model card keywords NMF and PMF specify the polarity of the transistor. The MESFET model is derived from the GaAs FET model described in H. Statz et al., GaAs FET Device and Circuit Simulation in SPICE, IEEE Transactions on Electron Devices, V34, Number 2, February, 1987 pp160-169.

Two ohmic resistances, Rd and Rs, are included. Charge storage is modeled by total gate charge as a function of gate-drain and gate-source voltages and is defined by the parameters Cgs, Cgd, and Pb.

NameDescriptionUnitsDefault
VtoPinch-off voltageV-2.
BetaTransconductance parameterA/V21e-4
BDoping tail extending parameter1/V0.3
AlphaSaturation voltage parameter1/V2.
LambdaChannel-length modulation1/V0.
RdDrain ohmic resistanceΩ0.
RsSource ohmic resistanceΩ0.
CgsZero-bias G-S junction capacitanceF0.
CgdZero-bias G-D junction capacitanceF0.
PbGate junction potentialV1.
KfFlicker noise coefficient-0.
AfFlicker noise exponent-1.
FcForward-bias depletion coefficient-0.5
IsJunction saturation currentA1e-14

A device with a Z as prefix can also mean an IGBT transistor. Disambiguation between the MESFET and IGBT is via the model statement.

Syntax: Zxxx C G E MNAME [area] [m=<value>] [off] [temp=<value>]
        .model MNAME NIGBT

The LTspice IGBT implementation is based on original work by Robert Ritchie of Linear Technology Corporation. It uses device equations out of a series of papers by Allen Hefner of NIST et al. with some exceptions, e.g., the LTspice implementation includes subthreshold conduction and stochastic noise mechanisms.

NameDescriptionUnitsDefault
AgdGate-Drain overlap areaA/V25e-6
areaActive aream21e-5
BVFAvalanche uniformity factor-1.
BVNAvalanche multiplication exponent-4.
CgsGate-Source capacitance per unit areaF/cm21.24e-8
CoxdGate-Drain oxide capacitance per unit areaF/cm23.5e-8
JsneEmitter saturation current densityA/cm26.5e-13
KFTriode region factor-1.
KPMOSFET transconductanceA/V2.38
MUNElectron mobilitycm2/(V·s)1500
MUPHole mobilitycm2/(V·s)450
NBBase doping1/cm32e14
TauAmbipolar recombination lifetimesec7.1e-6
ThetaTransverse field factor1/V0.02
VtThreshold voltageV4.7
VtdGate-Drain overlap depletion thresholdV1e-3
WBMetallurgical base widthm9e-5
subthresSubthreshold current parameter-.02
KfnFlicker noise coefficient-0.
AfnFlicker noise exponent-1.
tnomParameter measurement temperature°C27