how to calculate the drain cap in cadence

[Julian18]

Hi, there
I want to get the drain cap of a common CS MOS amplifier, after dc analysis, the cadence calculated cdd, cdg,cdb,cds, but i dont know which one i should use to calcuate the bandwidth at the drain node, suppose the drain node seeing some resistance.


Thanks.

 

[cpt]

I suppose you should use Cdd, which is the sum of Cdb+Cds+Cdg.

 

[markjiang]

remember to sum the capacitor of the loading transistor and amplifer transistor