AD797 Offset Nulling with zero-drift op-amp

dtm9991 on Apr 7, 2022

Hi Analog Engineers,

I see in the LT1028 datasheet (as well as in AN-21) that one can use a zero-drift amplifier to offset trim an amplifier. It is stated that this lowers the offset drift: from uV/C to nV/C (which is pretty amazing). I am guessing that this can be done with AD797 as well, only that you reference the negative supply versus the positive supply. Am I correct in assuming this is the way to do it, or that it can even be done with AD797?

Thanks,

Doug

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on Apr 8, 2022 3:14 AM
HI Doug,

I think the LT1028 is not the one that causes the offset drift to be 50nV/degC. LT1052 has guaranteed max offset drift of 50nV/degC

Regards,

Mon
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0 dtm9991 on Apr 8, 2022 6:48 PM in reply to ADIApproved

Hi Mon,

Yes, I agree the zero-drift LT1052 is providing the nice low offset drift of 50nV/degC. A better wording of my question is: can you use LT1052 to null offset trim another amplifier like AD797, just as shown you can with LT1028? AD797's offset trim references the negative supply, so asking to make sure I just use the same circuit only reference the negative supply.
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on Apr 19, 2022 2:42 AM in reply to dtm9991
Hi Doug,

The AD797 should still achieve the 50nV/degC specification for this setup.

Regards,

Mon
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