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Can Comparator's noise contribute to the white noise for oversampling SAR ADC?

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Erictsk

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I have some questions regarding to the noise definition for oversampling SAR ADC.
In order for oversampling to work, there must be some noise(~1 lsb rms) assuming to be white at the ADC's input to work.
On the other hand, the comparator inside the ADC has some intrinsic noise. so my question is, can the comparator's noise considered to be part of the white noise needed for the oversampling to work?
 

A little bit of circuit manipulation will indicate that yes, the comparator's noise contributes directly to the "input" noise, and therefore assists in meeting the criterion for oversampling. (One can imagine the comparator's input noise as a noise voltage source Vnoise in series with the ideal comparator's input; the voltage seen by the ideal comparator is then Vin + Vnoise).

One should not assume, however, that the comparator's noise is fully white; its spectrum is likely pink.
 

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