Hi,

I tried to examine (using spectre) to which freqency pinched MOSFET (BSIM3v3 model) acts as constant current soure. I gave constant dc bias on gate, dc bias on drain and superimposed ac voltage to drain and examined drain current.
I've expected capacitive current through drain to be w*Cdd*Vac, but it was 4-times bigger. Is the way I'm computing expected capacitive current wrong or why is there that difference?

thanks
miro

Hi,

As far as i remember from circuit theory lessons (it's been soooo far away), the admitance of capacitor is w*C so current should be w*Cdd*Vac=2*pi*f*Cdd*Vac.
I think the problem could be that i shouldn't use Cdd but some different capacitance(but which?)

miro

Try looking at the posts by Andrew Beckett on MOSFET capacitances as reported by Spectre. You can find them at
http://www.designers-guide.com/Forum/?board=analog_design;action=display;num=108...

- MM -