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Simulators >> RF Simulators >> Parasitic resistors problem of NMOS switch in pnoise simulation in simple S&H
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Message started by OmerNuz on Aug 18^th, 2015, 4:15am

Title: Parasitic resistors problem of NMOS switch in pnoise simulation in simple S&H
Post by OmerNuz on Aug 18^th, 2015, 4:15am

Hi,

I have a problem with parasitic noise sources of rs & rd of NMOS switch in simulating the simple sample and hold circuit noise with pnoise. When I look at the noise sources from noise summary, I see that in addition to id noise of NMOS switch, there are two other noise sources rs & rd.

I saw that rs & rd noise changes with the pulse width of the clock but I could not find the reason for that noise? In some simulations, these are the dominant noise sources.

What is the reason for that noise or has anyone encountered this problem before?

Title: Re: Parasitic resistors problem of NMOS switch in pnoise simulation in simple S&H
Post by Ken Kundert on Aug 18^th, 2015, 3:59pm

rs and rd are parasitic resistors in series with the source and the drain. The noise you are seeing is the thermal noise they produce.

-Ken