Question about Class A and Class AB OpAmps

[terryssw]

Class A vs Class AB

I have some doublt on the use of Class A or AB opamps (in switched-cap applications). As Class A have high standby power (and high slew rate requirements), why don't all opamps designed as Class AB opamps which has very low standy by current and large slew rate provided? Thanks for every comments in advance.

 

[opamp741]

Re: Class A vs Class AB

I think the major issue with class AB is design complexity and nonlinearity.

 

[sunking]

Re: Class A vs Class AB

Class A is lower THD.

 

[Edward_2288]

Re: Class A vs Class AB

hi
well, there are some tradeoff you need to consider. that's why some ppl use class a, the others use ab

 

[terryssw]

Re: Class A vs Class AB

I have also heard that Class AB produce lesser THD than Class A because Class AB can increase the output current that charge large capacitve loads, while Class-A is slew rate limited and thus causing harmonic distortion. Is this true or not?

 

[goodboy_pl]

Re: Class A vs Class AB

One of the most important issues of class AB OPAMPS are bad input matching of the opamp which requires large devices and therefor a little lower speed.
another issue is design complexity; since it is nonlinear, its design flow, is more or less empirical which means a lot of tray and error!

as I know nonlinearity behevior of them is not important in Switched Capacitor Ckts but is important in Contious signal processing Ckts like GmC filters.

BEST!