Hello everyone! Lately I have simulated fully differential OTA with chopper stablization circuits. I need to get SNR of output waveforms. The first methd of getting SNR is that I simulate it by tran noise simulation and I can get the output waveforms, after FFT transforming, I can read the result of SNR. The second way is PSS simulation. And I can get the spectrum of noise then by some mathematical calculation I can get the SNR. But these two ways attain two different results. I don't know which way of simulation is accurate. I hope that I can get yours answers. Thank you!

Hi, Sheldon!
       Thanks for your reply. I appreciate your time. At present, I just consider the performance of reconstruction filter. I think that the fully differential OTA with chopper stablization can be stable after several microseconds when the beating frequency of PSS and PNOISE simulation interface is chopper frequency.
       Do you mean that the second way to get SNR is not accurate? If so, how can I simulate noise performance of reconstruction filter and get the SNR?