prcken
Junior Member
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Posts: 18
PRC
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Hello, I am so confused. i am designing a fully differential opamp with precision gain of 2 used in pipeline ADC, when i replaced SC CMFB with ideal CMFB to do AC analysis in continuous time, i could get 66dB open loop gain of the opamp, then i put it in the switched-cap application, use pss+pstb to characterize the loop gain, it drops to about 20dB at 50MHz sampling rate. i also tried and compared with PAC simulation for opamp open loop gain. it indeed shows gain drops as increasing sampling rate. is that reliable to use PSTB and PAC to check the gain? Looking forward to your reply. Thanks!
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