# Folded-cascode random input offset voltage

1. ## folded cascode offset

Hello,

Anybody knows how to calculate the random input offset voltage of the folded-cascode operational amplifier by hand?
I need to find 3sigma offset, knowing sigma beta and sigma threshold according to the Pelgrom model.
If you know some literature, please tell me.
Thank you. •

2. ## input offset folded cascode amp

mm...
I think Razavi' book is very clear, reference the chapter about nonlinearity and match.
For folded cascode, the offset are mainly from input pairs and active current source. •

3. ## folded cascode matching

Check the book Design of Low-Voltage Low-Power Operational Amplifier Cells by Ron Hogervorst. Also check this pdf. It has all the Pelgrom's equations and offset equations for the folded cascode OTA.

http://www.utdallas.edu/~hellums/doc...7/Matching.pdf •

4. ## how to calculate offset voltage Originally Posted by gsuarez
Also check this pdf. It has all the Pelgrom's equations and offset equations for the folded cascode OTA.

http://www.utdallas.edu/~hellums/doc...7/Matching.pdf

I have some doubt about this article. Especially, I was laughing, when in section 5.2 author chose length of transistor 20um and 32um :)). 5. ## folded cascode offset calculation

assuming that the transconductance of input pair is large compared to that of load, the mismatch of input pair is the random offset --[[ ]]--