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.
| Name | Description | Units | Default |
| Vto | Pinch-off voltage | V | -2.0 |
| Beta | Transconductance parameter | A/V2 | 1e-4 |
| B | Doping tail extending parameter | 1/V | 0.3 |
| Alpha | Saturation voltage parameter | 1/V | 2.0 |
| Lambda | Channel-length modulation | 1/V | 0.0 |
| Rd | Drain ohmic resistance | Ω | 0.0 |
| Rs | Source ohmic resistance | Ω | 0.0 |
| Cgs | Zero-bias G-S junction capacitance | F | 0.0 |
| Cgd | Zero-bias G-D junction capacitance | F | 0.0 |
| Pb | Gate junction potential | V | 1.0 |
| Kf | Flicker noise coefficient | - | 0.0 |
| Af | Flicker noise exponent | - | 1.0 |
| Fc | Forward-bias depletion coefficient | - | 0.5 |
| Is | Junction saturation current | A | 1e-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.
| Name | Description | Units | Default |
| Agd | Gate-Drain overlap area | A/V2 | 5e-6 |
| area | Active area | m2 | 1e-5 |
| BVF | Avalanche uniformity factor | - | 1.0 |
| BVN | Avalanche multiplication exponent | - | 4.0 |
| Cgs | Gate-Source capacitance per unit area | F/cm2 | 1.24e-8 |
| Coxd | Gate-Drain oxide capacitance per unit area | F/cm2 | 3.5e-8 |
| Jsne | Emitter saturation current density | A/cm2 | 6.5e-13 |
| KF | Triode region factor | - | 1.0 |
| KP | MOSFET transconductance | A/V2 | 0.38 |
| MUN | Electron mobility | cm2/(V·s) | 1500 |
| MUP | Hole mobility | cm2/(V·s) | 450 |
| NB | Base doping | 1/cm3 | 2e14 |
| Tau | Ambipolar recombination lifetime | sec | 7.1e-6 |
| Theta | Transverse field factor | 1/V | 0.02 |
| Vt | Threshold voltage | V | 4.7 |
| Vtd | Gate-Drain overlap depletion threshold | V | 1e-3 |
| WB | Metallurgical base width | m | 9e-5 |
| subthres | Subthreshold current parameter | - | 0.02 |
| Kfn | Flicker noise coefficient | - | 0.0 |
| Afn | Flicker noise exponent | - | 1.0 |
| tnom | Parameter measurement temperature | °C | 27 |