vivkr
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Hi,
The classic paper by Bult and Geelen on gain-boosting amps "A Fast Settling CMOS Op Amp for SC Circuits with 90-dB DC Gain," JSSC, Dec. 1990 presents measurement results of the gain and phase response of the prototype opamp.
How do they actually measure the gain of such a high-gain opamp.
Signal ~ 4V, Gain ~ 90 dB => vin(diff) ~ 100uV.
Offset alone would make it very difficult to do an "open-loop" input-output gain measurement.
As a student, I trimmed offsets of some old-fashioned BJT opamps once or twice using resistive pots. However, the approach is not very easy to implement and it would be hard to measure several different chips. How would one get rid of the offset while measuring the gain of such a high-gain CMOS opamp.
In fact, how would one actually do the lab measurement of such a high gain opamp even if there were no offset. In simulations, one can do this very easily, but perhaps there is a good method for measurements too.
Could someone suggest a good method ?
Thanks Vivek
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