PSRR in op amp

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jsnx

Joined Mar 17, 2022
21
Hello, I have a question about the PSRR and the noise in an op amp.

Which configuration has the best PSRR? Is it the telescopic one or the folded cascode? I know that to improve PSRR, we need to have a high output resistance and symmetric architecture ( can someone pls tell me why symmetry play a role in PSRR?). From this information, the telescopic seems to be the best one no?

Also, when it comes to noise, is it better to have a CMOS op amp or to use BJT? I can't tell which type of transistor is the noisiest. Sometimes I find websites saying that it is BJT because it's a bipolar device ( and so both carriers are affected by any variations), others say that BJT is better than MOSFET in analog circuits

Thank you in advance
 

Ian0

Joined Aug 7, 2020
5,162
Also, when it comes to noise, is it better to have a CMOS op amp or to use BJT? I can't tell which type of transistor is the noisiest. Sometimes I find websites saying that it is BJT because it's a bipolar device ( and so both carriers are affected by any variations), others say that BJT is better than MOSFET in analog circuits
A MOSFET op amp is generally noisier than both JFET and bipolar op-amps.
JFETs will be quieter than bipolar for a high source impedance, and bipolar will be quieter than JFETs for a low source impedance.
Never forget to add the current noise to the calculation!
 
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