question about the requirement of opamp used in the ADC

[rocshrike]

Do we need the -3dB frequence of opamp greater than the signal frequency?
To reach a give resolution of Nyquist ADC, the DC gain of opamp must be greater than 2©(N-1), (according the book "mix signal design" by Baker), but if the -3dB frequency of opamp is smaller than the signal frequency, which means for this signal frequency, the gain is not enough to reach the required resolution.

 

[wsy979]

i think it is not a must
i have done an OTA for S/H,it seems that the -3db bandwidth doesnot affect the error

 

[sunking]

yes, it should greater than the signal frequency.
Or it will generate gain error and INL&DNL

 

[wsy979]

to dear sunking

could u plz explain how the the -3db bandwidth generate the gain error
or plz tell me what should i refer to for finding out the explanation
thx

regards