Single-ended CMOS Cascode OpAmp Design

[nickagian1]

Can anybody help me with the following circuit? As you can see it is about a CMOS OpAmp, with cascode input stage. I want to find a way to bias M3,M4 (Vb) but until now I cannot manage it. Can anybody suggest me a solution for biasing and how to calculate it (I mean the W/L ratio of the MOSFETs used, considering that I want a current of 1.5mA on both M1 and M2 tails and a bias voltage Vb of about 2V).

View attachment 39539

 

[MP1]

Homework assignment?

MP

 

[nickagian1]

Yeap... I have to design a whole 2-stage CMOS OpAmp... and still haven`t find a solution.