Issue with VFWD Parameter in Diode Model Not Reflected in Simulation

[sujith]

Hello,

I’ve modeled a simple diode circuit in QSPICE to test the VFWD parameter in the .model directive. However, I’ve noticed that setting VFWD=0.3 has no effect on the output voltage. The output remains around 0.831 V, regardless of whether the VFWD parameter is specified or omitted. You can see this behavior in the attached schematic and simulation plot.

According to the documentation, the VFWD value should define the forward voltage drop, but that doesn’t seem to be happening here. Interestingly, the VREV parameter does appear to work as expected.

It would be really helpful if someone could confirm whether this is a tool limitation or if I’m missing something in the modeling process. Fixing this or providing a workaround would really help as I continue with modeling more complex circuits.

Thanks in advance!

[bordodynov]

You must specify a Ron value that is not equal to 0.

[KSKelvin]

Here is a reference from the Qspice Help, as explained by @bordodynov in previous post.

[sujith]

Thank you so much for your swift and helpful response it helped.

[sujith]

Thank you so much for your response and I am glad that it resolved quickly.