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why ADC always choose SC cmfb

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iexplorer

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I have never seen a ADC use resist divider cmfb ,why? Besides area consideration
 

castrader

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sc cmfb will generate great equivalent resistance, so that it will not affect the output stage gain.
Also by sc cmfb, other voltage than vcm can be feedback to the op, so that one cmfb op can be saved to enhance the cmfb gbw.
The most fundermental reason is that: ADC is a discrete time block, it has clock, so sc cmfb can be realized without defect.
 

    iexplorer

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jeffsky520

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1, Save your power
2, Signal swing limit free
 

    iexplorer

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lijianheng

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Larger resistor by SC, it doesn't affect the differential ac performance.
 

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