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"Check For Op Amp DC Offset Shift," John Dunn, Electronic Design, March 4, 1993.
I've used this trick before to check servos that don't have a passive pole at the input (thanks JR) as well as using it as a general op amp evaluator.
When slow DC-precise op amps or fast ones with asymmetric slewing are presented with high frequency inputs there is rectification.
This is of particular concern when op amps having this characteristic are used as servos.
"Check For Op Amp DC Offset Shift," John Dunn, Electronic Design, March 4, 1993.
Check For Op Amp DC Offset Shift," John Dunn Electronic Design, March 4, 1993. Full pdf: https://proaudiodesignforum.com/images/ ... 4_1993.pdf
How does your favourite cheapo OP07 do in this test?
The OP07 does OK as a simple integrator-type servo if the input R is relatively high and Cfb relatively small. viewtopic.php?f=6&t=419&p=4999
IIRC with an OP07 the DC shift isn't as pronounced as the rising output response with frequency.
Too small R or too big C and it doesn't have enough current and/or BW and the output becomes "inductive."
But it still has some DC shift...
With a passive pole at the input the OP07 can be made to work very well.
