In this article we’ ll see how to find the parameters used to describe the mathematical behaviour of JFET (Junction Field Effect Transistors).The syntax for the N-channel model is:
model ModelName NJF( par1=a par2=b………parn=x)
while for the P-channel model is:
model ModelName PJF( par1=a par2=b………parn=x)
Where par1 par2… parn are the parameters that allow us to model the equations of the JFET transistor.
The main parameters for modeling the JFET are listed below in this table:
| Parameters | Description | Units | Default Value |
|---|---|---|---|
| AF | Flicker noise exponent | no unit dimension | 1.0 |
| ALPHA | Ionization coefficient | 1/V | 1e-006 |
| BETA | Transconductance coefficient | A/V^2 | 0.0001 |
| BETATCE | BETA exponential temperature coefficient | %/°C | -0.5 |
| CGD | Zero-bias gate-drain p-n capacitance | F | 1e-012 |
| CGS | Zero-bias gate-source p-n capacitance | F | 1e-012 |
| FC | Forward-bias depletion capacitance coefficient | no unit dimension | 0.5 |
| IS | Gate p-n saturation current | A | 1e-014 |
| ISR | Gate p-n recombination current parameter | A | 0 |
| KF | Flicker noise coefficient | no unit dimension | 1e-018 |
| LAMBDA | Channel-length modulation | 1/V | 1e-006 |
| M | Gate p-n grading coefficient | no unit dimension | 0.5 |
| N | Gate p-n emission coefficient | no unit dimension | 1.0 |
| NR | Emission coefficient for ISR | no unit dimension | 2.0 |
| PB | Gate p-n potential | V | 1.0 |
| RD | Drain ohmic resistance | Ohm | 1.0 |
| RS | Source ohmic resistance | Ohm | 1.0 |
| VK | Ionization knee voltage | V | 1.0 |
| VTO | Thresold voltage | V | -2.0 |
| VTOTC | VTO temperature coefficient | V/°C | -0.0025 |
| XTI | IS temperature coefficient | no unit dimension | 3.0 |