How a folded cascode can help to improve the cutoff frequency of a CMOS transistor?

Hi all,

I am in the myst of prove how a folded cascode configuration can help to improve the cut off frequency of a CMOS transistor. I need formula to proof how this is happened?

Anyhow, formula or intuition explanation or any other positive explanation are appreaciated.

Thanks a lot!

The point is that you can reduce your Cgs to half to improve the cut-off frequency since Ft=gm/cgs.

Hi nxing,

Can i know how to reduce Cgs to half?

Do you mean the size of transistor can be reduced to half in order to reduce the Cgs to half?

Thank you

No, If I understand correctly, you will have to most gate in parallel and this will reduce the cgs to half.

adding a cascode isolates the output node from the input node and thereby removing the miller cap from being seen at the output node, hence the improved freq performance. Cascode also provides more gain by increasing effective output impedance. Hope this helps.