Biasing Fully Differential Amplifier with folded cascode

[firasgany7]

Hi Guys,
I'm trying to design the op amp in the attached article.
I'm using 100uA current source and I'm trying to make a bias circuit in order to make all transistors in saturation and I don't know how to make that.






differential input is +-0.5v.
common mode input: 1v
and I used the W/L ratios for the transistor from the article.

Thanks,
Firas

 

[Sambhav_1]

Hi,
For designing current mirrors, you should not use a ideal current source because you can get into trouble while replacing that current source.
I dont know about the VDD value of your technology but you can simply start with a resistor ladder instead of current source and then copy the current.
For biasing circuit, you can go with stacked transistors(or search for advanced current mirrors) which will help you in designing your biasing circuit.
Since you have not mentioned what gain value you are targeting, it would be good if you start with minimum biasing current(like 10uA), then you can increase the size accordingly.
Thanks