[question from student] How to find a load capacitance of CMOS inverter?

[vadim888]

Dear all,

I just want to understand, how to find CL?

Because for sizing CMOS inverter you always need to know load capacitance, but in real layout or schematic you don't have any capacitance instance.

I have one idea, maybe it's a parasitics capacitance, but how I can find it, from PDK?

Regards,
Vadim

 

[erikl]

It's the sum of output capacitance of the inverter, the routing parasitics, and the input capacitance of the following stage or cell to be driven.