CMRR & PSRR requirement

[suria3]

Hi Guys,

I'm desigining an high gain opamp for a application in a feedback loop like in common mode feedback circuit. Since, this opamp is in the feedback loop, which is a low frequency application, my question is what is the value in dB I should design for both the CMRR and PSRR of this opamp. Is it the PSRR need to be at least 50dB at 1MHz and so on. Please give ur suggestion.

Thanks,
Suria

 

[tedd]

if the opamp is used in dc applications such as bandgap, i think psrr=50db at 1Mhz is not necessary,unless the circuit is disturbed by high frequency noise. of course, in high gain opamp, the psrr also is very high, if the bandwidth is set to high value, it is not hard to get psrr=50db in 1MHZ