In the Nonlinear Diode model in Keysight Genesys there is no forward bias voltage parameter. There is a "junction potential" (Vj) parameter, however. I've never seen or heard anyone use the term junction potential to describe a diode property though. Is it the same thing as forward bias voltage?


1 Answer 1


The VJ parameter is used by many SPICE-derived simulators for their diode models. It doesn't affect the I-V characteristics of the diode, but rather the capacitance characteristic.

The junction capacitance characteristic is given by



The total capacitance of the diode is


with \$C_j\$ being dominant when the diode is reverse biased, and the diffusion capacitance \$C_d\$ being dominant when the diode is forward biased.

If you want to set the forward voltage of the diode, you need to look at the Shockley diode equation

$$I(V) = I_s \exp\left(\frac{V}{nV_T}-1\right)$$

and set the corresponding SPICE parameters IS and N (and possibly the series resistance RS) to achieve the forward voltage (and reverse leakage) to match your physical diode.


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