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Simulators >> RF Simulators >> Questions about Switched capacitor circuits simulation with PSS+PNOIS
https://designers-guide.org/forum/YaBB.pl?num=1249508809

Message started by lunren on Aug 5^th, 2009, 2:46pm

Title: Questions about Switched capacitor circuits simulation with PSS+PNOIS
Post by lunren on Aug 5^th, 2009, 2:46pm

Hi,

Today I simulated my swiched capacitor circuit (sample and hold) with pss+pnoise. In the simulation, the switched capacitor common mode feedback circuit was replaced by a ideal one. I am wondering how to use the real swiched capacitor CMFB in my simulation?

Why I was confused by this? Because SC-CMFB will take some time to settle down. I am not sure if I use the real SC-CMFB, the simulation results is culculated at correct DC operating point or not. Hope someone can give me some hints about this.

Thanks,

Lunren

Title: Re: Questions about Switched capacitor circuits simulation with PSS+PNOIS
Post by thechopper on Aug 5^th, 2009, 5:50pm

Hi,

You SHOULD use the real CMFB circuit. PSS takes care of looking for the steady state value, meaning that it will iterate as much as it needs until it finds a stable periodic operating point.
Only after finding such point it will start pnoise analysis.

Hope this helps
Tosei

Title: Re: Questions about Switched capacitor circuits simulation with PSS+PNOIS
Post by lunren on Aug 5^th, 2009, 6:15pm

So that means I do not need to set tstart=50u, for example (assuming cmfb settles down after 50us)?