I have tested two AD8421ARZ with gain 991 (Rg=10). Power Supply +/-5V. Both inputs connected to gnd through 2k.
One amplifier has offset 21mV, the other has 5mV. Is this difference between amplifiers normal?
I'm assuming you are measuring at the output? If so, the input offset for the A part is 60uV
and the output offset is 350uV, so 60uV*991 = 59460 + 350 = 59810uV = 59.8 mV.
21 mV sounds good.
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