Symbol Names: NJF, PJF
Syntax: Jxxx D G S <model> [area] [off] [IC=Vds, Vgs] [temp=T]
Examples:
J1 0 in out MyJFETmodel
.model MyJFETmodel NJF(Lambda=.001)
J2 0 in out MyPJFETmodel
.model MyPJFETmodel PJF(Lambda=.001)
A JFET transistor requires a .model card to specify its characteristics. Note that the model card keywords NJF and PJF specify the polarity of the transistor. The area factor determines the number of equivalent parallel devices of a specified model.
The JFET model is derived from the FET model of Shichman and Hodges extended to include Gate junction recombination current and impact ionization. The DC characteristics are defined by the parameters VTO and BETA, which determine the variation of drain current with gate voltage; LAMBDA, which determines the output conductance; and Is, the saturation current of the two gate junctions. Two ohmic resistances, Rd and Rs, are included. Charge storage is modeled by nonlinear depletion layer capacitances for both gate junctions; which vary as the -1/2 power of junction voltage and are defined by the parameters Cgs, Cgd, and PB. A fitting parameter B has been added. See A. E. Parker and D. J. Skellern, An Improved FET Model for Computer Simulators, IEEE Trans CAD, vol. 9, no. 5, pp. 551-553, May 1990.
| Name | Description | Units | Default | Example |
| Vto | Threshold voltage | V | -2.0 | -2.0 |
| Beta | Transconductance parameter | A/V2 | 1e-4 | 1e-3 |
| Lambda | Channel-length modulation parameter | 1/V | 0 | 1e-4 |
| Rd | Drain ohmic resistance | Ω | 0. | 100 |
| Rs | Source ohmic resistance | Ω | 0. | 100 |
| Cgs | Zero-bias G-S junction capacitance | F | 0. | 5p |
| Cgd | Zero-bias G-D junction capacitance | F | 0. | 1p |
| Pb | Gate junction potential | V | 1. | 0.6 |
| m | Gate junction grading coefficient | - | .5 | 0.8 |
| Is | Gate junction saturation current | A | 1e-14 | 1e-14 |
| B | Doping tail parameter | - | 1 | 1.1 |
| KF | Flicker noise coefficient | - | 0 | |
| Nlev | Noise equation selector | - | 0 | 3 |
| Gdsnoi | Shot noise coefficient for nlev=3 | - | 1. | 2. |
| AF | Flicker noise exponent | - | 1 | |
| Fc | Coefficient for forward-depletion capacitance | - | .5 | |
| Tnom | Parameter measurement temperature | °C | 27 | 50 |
| BetaTce | Transconductance parameter exponential temperature coefficient | %/°C | 0 | |
| VtoTc | Threshold voltage temperature coefficient | V/°C | 0 | |
| N | Gate junction emission coefficient | - | 1. | |
| Isr | Gate junction recombination current parameter | A | 0. | |
| Nr | Emission coefficient for Isr | - | 2 | |
| alpha | Ionization coefficient | 1/V | 0 | |
| Vk | Ionization knee voltage | V | 0 | |
| Xti | Saturation current temperature coefficient | - | 3 | |
| mfg | Annotation of manufacturer | - | 3 | ACME Semi Ltd. |