weak inversion parasitical caps

[mmarj]

Hello,

I have a question about parasitical caps (cgd, cgs, cgd,..) when mos is working in weak inversion do we see any different wrg to deep saturation region? is there any curve such cgs versis vgs,..?

 

[Dominik Przyborowski]

MOSFET can be in deep saturation and weak inversion in the same time - you are mixing terms. Also, capacitances mentioned by you, are not parasitic but inherent.

Anyway, yes there are a relations between inherent capacitances of MOSFET and it operating point. Briefly, they are higher in weak inversion then in strong. It is reflected in transit frequency, which is linear (in first order) function of inversion level and reaches maximum in strong inversion.