Hello to the community,
I am trying to do a PEX for some varactors that I have in my design, and the post layout simulation results are weirdly inaccurate. I feel like the Quantus tool disregards my varactor instance and calculates the parasitics as if I just had the metal layers I added myself in the layout view.
A simulation of the varactor in schematic view with Spectre shows that my capacitance changes between 190 fF and 450 fF when I change the DC voltage around my varactors, but when I add the dspf file generated by Quantus, my capacitance drops to 1 fF independently of the DC voltage value ! on the Quantus window, I choose transistor dspf as an output type, I don't know if this is the issue but I tried some other types of output and none of them seems to give an answer to my problem. Could someone advise me on what output type I should choose for something like a varactor, which is not a transistor but also technically not a passive element ? I would be grateful.
Thank you very much,
Youssef Bendou