Whats the difference between Cjd and Cdb ?

About Cgs..?

Hi, all....

I am curious that Cgs (or other capacitances...Cgd, Cgg,...etc) are actual capacitance value. I think those Cgs, Cgd...etc are different from our typical text book (like Razavi's). What do you think?
I heard that those are for small signal capacitance, which means they are biased at certain voltage and they are measured by wiggling (small voltage) one side of node. That's why they have wierd expression like Cgs and Csg or even negative sign. (I think these capacitances are called 'transcapacitances'??)

In spectre case, I also found 'Cjd' and 'Cjs' and I think they are not 'small-signal' capacitances.

Can anyone explain clearly what's going on?? I looked the manual and I couldn't find useful information...

If you refer any manual or paper or website....it would be even better...


To make a long story short, what's difference between Cjd and Cdb in spectre operating point parameters? In the text book, Cjd can be modeled as a part of Cd. (Cjd: drain-bulk junction cap). Why Cjd is much bigger than Cdb in most cases??





Thanks...

Re: About Cgs..?

pls check hspice manual, there is a section on transcapacitances