Dear Michael, thank you If I make circuit without op ampl buffer, then voltage acrsss R5 resistor (caused by the current from the ADC input) will be about 30k x 1 microA = 30 mV. I need to measure only AC component. In principle, I would consider this a permanent component (30 mV) in the time, when an alternating current by the sense resistor R1 is not flow. Alternating current flows through the sense R1 resistor is not always - there are times when it does not flow. All the more so, the divider R4, R5 too will not provide precisely 2,5 volts in an average point (since I'm going to take 5% resitors). Measurement accuracy of 10-15% of AC component is enough for me. If I do so, I can give up the op amplifier ? Or there are other issues that still require an op ampl? TIA Sincerely Vladimir Naumenkov www.agat.by
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