Hello everyone, how can I calculate the internal parameters of the transistor using Xschem tool (gf180 PDK).

Internal model parameters for bsim4 mos devices are documented in ngspice user manual chapter 31.6.9. Following example shows the syntax for saving some mos parameters like gm, gds, vth, vdsat and some capacitances. Don't ask me why these capacinatce values are negative and/or what these exactly mean. This can be answered by some bsim4 guru.

The negative value of capacitance has always bothered me with the BSIM4 models. What is really strange, not all values of capacitors are reported as negative values. This is just an artifact of the BSIM4 models. In my opinion, ignore the negative value. Also, complain loudly to the transistor modeling people. If someone could create a negative value capacitor in real life, we would have either an infinite energy source, or a black hole.

Regulating a negative capacitor for free energy extraction and preventing runaway is a tough task.... 😄😄

Thank you, a lot, for this. regarding the values of the capacitors, are they only annotated or reported as negative values and the actual values are normally positive?

@Mohamed Amr This is a 100000$ question. The BSIM4 models are quite complex, I don't know if the absolute value of these capacitances are meaningful or not, and I also don't know the difference between -for example- Cgs and Csg

I agree with Stefan Schippers. He has summed up the situation pretty well.