subgold
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I have a question concerning the PSRR of the bandgap.
I have a sub-1V current summing bandgap topology. I use a cascode transistor in the output branch to improve the PSRR.
then I add a regulation loop around the cascode transistor (gain-boosting) to further improve the PSRR. Then the problem arises. The PSRR improvement can only go up to a certain level, and can go no more higher, even if I increase the gain of gain-boosting amplifier, which would theoretically increase the output impedance of the cascode branch.
Also, the loop composed by the opamp has a rather high gain and PSRR, which doesn't seem to be the limiting factor here, does it? i am not so sure how this loop will eventually impact the PSRR.
Can anybody give me a clue on what is limiting the PSRR in this case? Thanks a lot.
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