rise time and fall time of the cell

[owen_li]

Hi all.

Can you tell me why we should equate the rise time and fall time of a standard cell ?

Like a inverter, we usually draw a pMos 2 times wider than nMos to ensure the rise time is matching the fall time.

Thanks!

 

[vijay.mani884]

This is done to equalise the switching time of both nmos and pmos.. that is charging and discharging of the output cap at the same rate..

Cheers