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AD7124 zero offset problem

Question asked by majkls on May 13, 2018
Latest reply on May 28, 2018 by majkls

Hello, I have a problem with integrating my circuit with AD7124 IC. When I shorten the inputs of the OP-amp circuit driving the ADC, ADC shows that there is a 0,95 mV offset. However when I measure voltage on input capacitor between AIN2, AIN3 (my differential pair) I got something like 0,09mV (corresponds to offset of the OP-AMP). When I apply voltage on the input of the OP-amp circuit (roughly 4 mV) I got offset which corresponds to 0,09 mV so the function seems to be correct. Even if I apply voltage as small as 0,4 mV to the input of OP-amp I got correct offset of OP-amp about 0,09mV.

 

Do you have any ideas about this problem?

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