A Question About Opamp Design

[naalald]

What is a good structure for the opamp used in a switched-capacitor integrator?
I've seen that folded-cascode and class AB opamps are so common. But for a low-voltage and low-power design, what are the benefits and drawbacks of the two structures? Do you recommend any other structure(s)? Why?
Thanks.

 

[supreet_95]

Folded cascode are better as they provide high gain and also a high common mode voltage range. U can independently increase the 2nd stage current to decrease the slew rate dependent settling time and 1st stage gain to decrease bandwidth limited settling time.
As if the switched cap circuits are working at 3MHz then the settling time can be only 150ns.
Hope this helps.

 

[cathyyang]

i agree with above. but, in other aspect, general fold cascode may need high supply voltage, so if you use fold cascode for low-voltage, you should design low-voltage structure.