chungmnig
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Hi~ I simulate noise of a fully differential OPA switch cap structure using spectre Pnoise . I have some problems First i use PSS and Pnoise analysis , then i want to see input referred noise , and it is impractical small , just about 20nV/Hz (better than IEEE papers so imust some where wrong.......) my clock 2MHz so i set PSS maxacfreq=240M and Pnoise max sideband =100 , i think it is enough. i had read Simulating switched-capacitor filters with SpectreRF , so i think other settlings is correct. input reffered noise = (output noise)/(Transfer function) is right? i see output noise , input noise,transfer function of Pnoise i think the former statement is right. and transfer fuction of Pnoise is the same as PAC analysis. So where i get wrong? How to measure right input referred noise?
Second i also using chopper to eliminate 1/f noise(chopper clock is 1MHz). The same simulation step like above. But the ttransfer function is wrong , it very small (minus dB) So the input refered noise is larger than output noise. My circuit is correct. could some body give me some suggestions about it ~~~ thanks~~
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