The NMOS in NWELL cap, from what I know is also called varactor by someone.  I'm trying to utilize such kind of capacitor in a 0.13um logic process while the model file is not provided by the foundry.  So DIY the model (if possible) is necessary.

By checking the varactor model from other process/fab, it seems a "NMOS in NWELL" cap can be modeled by using P-type BSIM model,  as long as the following param is revised , for example:

model PVAR bsim3v3 type=p
+version = 3.2 tnom = 25
+capmod = 3 voffcv = -0.015 k1 = 0.482
+vth0 = -1.33+dPVAR2 acde = 1.0 tox = 2.77E-9+dPVAR1
+toxm = 2.77E-9 nch = 2.77E+17 dskip = no
+binunit = 2 k2=0 kt1=0.08
ends PVAR

If the fab provide normal nmos/pmos BSIM model only(and without further modeling support from them) , is there a safe way to "convert to" a varactor model? How should I modify the BSIM model parameter , ie, which are the vital parameter that I have to know to specify a varactor model?

Thanks for all the help

I think Bsim3v3 model is not as simple as you think.
And it is of no sense if the model itself is not correct, especially for RF

bluestatic wrote on Dec 21^st, 2006, 1:18am: