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Question aboout switched-capacitor CMFB in switched-cap amp

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neoflash

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Feel a little difficult to derive the linear model for the switched-capacitor CMFB circuits.

Any suggestions or recommended tutorials.
 

Another question is that CMFB refreshing phase (phi-2) should be in the same time of integrator sampling or integration?

I guess doing the refreshing in integration phase make more sense, right?
 

Re: Question aboout switched-capacitor CMFB in switched-cap

where ever you got this pic. i think that is a good reference. i guess it is from "Analysis of Switched-Capacitor Common-Mode Feedback Circuit" by Ojas Choksi.
This paper is a very good reference.

Added after 2 minutes:

refreshing in the integration phase makes sense, me too think so.
 

Re: Question aboout switched-capacitor CMFB in switched-cap

neoflash said:
Feel a little difficult to derive the linear model for the switched-capacitor CMFB circuits.quote]
What do you mean by ''linear model''? Isn't the model proposed in the paper suitable?
Click to expand...
 

I realized that it doesn't matter which phase to refresh the cmfb. Becasue the input CM is not allowed to jump a lot during successive clock cycles, otherwise, the circuit can't work anyway.
 

Re: Question aboout switched-capacitor CMFB in switched-cap

Hello, neoflash

You explained the size of C1 and C2. If the size of C1 and C2 is wrong, input common mode voltage jumps and then settles.
 

Re: Question aboout switched-capacitor CMFB in switched-cap

hi guys what ever i try the capacitance values the output for a constant input is oscillating can any body help me with this issue. Thanks in advance. i need just a fully functioning circuit for the SC-CMFB to know and do a circuit like that.it's urgent guys please reply asap.
 

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