CMFB and Biasing Issues

[ahmed_hussein5]

Greetings,

I have built a Folded Cascode OTA with NMOS diff pair and made its CMFB circuit, feeding back at the Lowest NMOS pair biasing voltage,
the problem arising now is when I try to bias the NMOS pair above it using a current mirror to generate a reference bias. any Ideas on how to make such a bias?

Thanks in advance

 

[erikl]

Show your schematic, please!

If I understand your description correctly, instead of the lowest NMOS pair use a single NMOS which feeds both legs.

Or you could connect the CMFB generated bias to the PMOS load transistors. Correct DC level, of course.