JXXXXXXX ND NG NS MNAME <AREA> <OFF> <IC=VDS,VGS>
Example:
J1 7 2 3 JM1 OFF
ND, NG, and NS are the drain, gate, and source nodes, respectively. MNAME is the model name, AREA is the area factor, and OFF indicates an (optional) initial condition on the device for DC analysis. If the area factor is omitted, a value of 1.0 is assumed. The (optional) initial condition specification, using IC=VDS,VGS is intended for use with the UIC option on the .TRAN statement, when a transient analysis is desired starting from other than the quiescent operating point. See the .IC statement for a better way to set initial conditions.
JFET Models (both N and P Channel)
The JFET model is derived from the FET model of Shichman and Hodges. 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 non-linear 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.
JFET Model Parameters
| Name | Meaning | Units | Default | Area |
| VTO | threshold voltage | V | -2.0 | |
| BETA | transconductance parameter | A/V2 | 1.0E-4 | |
| LAMBDA | channel length modulation parameter | 1/V | 0 | |
| RD | drain ohmic resistance | W | 0 | * |
| RS | source ohmic resistance | W | 0 | * |
| CGS | zero-bias G-S junction capacitance | F | 0 | * |
| CGD | zero-bias G-D junction capacitance | F | 0 | * |
| M | gate junction grading coefficient | 0.5 | ||
| PB | gate junction potential | V | 1 | |
| IS | gate junction saturation current | A | 1.0E-14 | * |
| N | gate junction emission coefficient | 1 | ||
| ISR | gate junction recombination current | A | 0 | |
| NR | emission coefficient for ISR | 2 | ||
| ALPHA | ionization coefficient | 1/V | 0 | |
| VK | ionization knee voltage | V | 0 | |
| KF | flicker noise coefficient | - | 0 | |
| AF | flicker noise exponent | - | 1 | |
| FC | coeff for forward-bias depletion cap formula- | 0.5 | ||
| VTOTC | VTO temperature coefficient | V/°C | 0 | |
| BETATCE | BETA exponential temperature coefficient | %/°C | 0 | |
| XTI | IS temperature coefficient | 3 |
* The parameter scales with area.