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Design >> Mixed-Signal Design >> pnoise not showing 1/f noise attenuation
https://designers-guide.org/forum/YaBB.pl?num=1335662072

Message started by analog2000 on Apr 28^th, 2012, 6:14pm

Title: pnoise not showing 1/f noise attenuation
Post by analog2000 on Apr 28^th, 2012, 6:14pm

Hello,
I have a switched cap gain stage which has 1/f noise and dc offset cancellation circuit, it is driven by a 2 phase non overlap clock.
When I run pnoise analysis on it, I expect to see equivalent output noise spectrum showing attenuation at low frequencies but I do not ?

My pss and pnoise deck is attached below
Any recommendations would be greatly appreciated
thanks
analog2000

simulatorOptions options reltol=1e-3 vabstol=1e-6 iabstol=1e-12 temp=55.0 \ tnom=27 scalem=1.0 scale=1.0 gmin=1e-12 rforce=1 maxnotes=5 maxwarns=5 \ digits=5 cols=80 pivrel=1e-3 sensfile="../psf/sens.output" \ checklimitdest=psf

pss pss fund=16.384K harms=10 errpreset=conservative tstab=10u + annotate=status

pnoise ( out ) pnoise sweeptype=relative relharmnum=0 + start=0.1 stop=200 dec=20 maxsideband=50 iprobe=V7 + refsideband=0 annotate=status

Title: Re: pnoise not showing 1/f noise attenuation
Post by BackerShu on Jul 18^th, 2012, 10:26pm

Did you add ideal S&H circuit after the switch-capacitor state to check the noise performance?

Just in case you may have some testbench issues, please check a well written document on this site which covers how to simulate switched-capacitor circuit using SC filter as example.