icguy wrote on May 4th, 2008, 7:19pm:should the DC Gain be calculated as follow ? DC Gain > 20log10(2^10)+20log(1/f) f=feedback factor
Yes, that would be the min acceptable value for your amp gain.
[/quote]
I can Understand Rc Associated to the sample circuits, it is a Transistor-on resistance and sampling capacitance;Yet Ican't
understand RC of the amplifier you mentioned above . In addition, why the settling time accuracy is 99.999%(or 0.001%),some papers
just take 0.1% or 0.01%, Can the settling accuracy arbitrarily chosen? I am totally confused. [/quote]
From the small signal perspective, if the opamp had a BW much smaller than the RC time constant, it might not be able to respond fast enough in order to force the desired voltage across the sampling cap, simply because it could not provide enough current to it. Therefore the amp BW should be such that a fair number of time constants (9 may be) fit within the sampling time.
Sheldon also brought up a good point about slew rate, which is a large signal condition that your opamp will have to meet, apart from the ones mentioned above.
Hope this is a little bit more clear.
Regards
Tosei