Can I know the capacitance between two nodes of MOS ?

[Kim Soo Hwan]

Help me~

I want to know the capacitance between two nodes of MOS
without using the hspice function.

For example, the capacitance between gate and drain.

With AC simulation, I tried to get the value.
But I failed because the value also got the cap 'between gate and source'
and 'between gate and bulk'.

I want to get the capacitance only between gate and drain.

How can I ?

 

[sutapanaki]

put an ac source to the gate, another one to the source and a third one to the bulk. Insure proper dc biasing. Now G,S and B wiggle together and capacitance between them is bootstrapped out. Measure the ac current from the ac source connected to the gate. This should be enough.