BJT bipolar transistors require a certain number of parameters to get a good model.The syntax for this model is:
.model ModelNameNPN (par1=a par2=b………parn=x)
for PNP case:
.model ModelNamePNP (par1=a par2=b………parn=x)
where par1 par2…….parn are the parameters that allow to model equations of the BJT.
The main parameters for a reasonable modeling of the behavior of the component are summarized in the following table:
| Parameters | Description | Units | Default Value |
|---|---|---|---|
| IS | Transport saturation current | A | 1e-16 |
| XTI | IS temperature effect exponent | no unit dimension | 3.0 |
| EG | Bandgap voltage (barrier height) | eV | 1.11 |
| VAF | Forward Early voltage | V | Infinite |
| BF | Ideal maximum forward beta | no unit dimension | 100 |
| ISE | Base-emitter leakage saturation current | A | 0 |
| NE | Base-emitter leakage emission coefficient | no unit dimension | 1.5 |
| IKF | Corner for forward-beta high-current roll-off | A | Infinite |
| NK | High-current roll-off coefficient | no unit dimension | 0.5 |
| XTB | Forward and reverse beta temperature coefficient | no unit dimension | 0 |
| BR | Ideal maximum reverse beta | no unit dimension | 1.0 |
| ISC | Base-collector leakage saturation current | A | 0 |
| NC | Base-collector leakage emission coefficient | no unit dimension | 2.0 |
| IKR | Corner for reverse-beta high-current roll-off | A | Infinite |
| RC | Collector ohmic resistance | Ohm | 0 |
| CJC | Base-collector zero-bias p-n capacitance | F | 0 |
| MJC | Base-collector p-n grading factor | no unit dimension | 0.33 |
| VJC | V | 0.75 | |
| FC | Forward-bias depletion capacitor coefficient | no unit dimension | 0.5 |
| CJE | Base-emitter zero-bias p-n capacitance | F | 0 |
| MJE | Base-emitter p-n grading factor | no unit dimension | 0.33 |
| VJE | Base-emitter built-in potential | V | 0.75 |
| TR | Ideal reverse transit time | sec | 1e-8 |
| TF | Ideal forward transit time | sec | 0 |
| ITF | Transit time dependency on Ic | A | 0 |
| XTF | Transit time bias dependence coefficient | no unit dimension | 0 |
| VTF | Transit time dependency on Vbc | V | Infinite |
| RB | Zero-bias (maximum) base resistance | Ohm | 0 |