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low current measurement using AD8421

Question asked by b.bosquet on Oct 28, 2017
Latest reply on Nov 9, 2017 by b.bosquet



I need to measure a current passing through a load (about 500kOms). This load is supplied by a sinusoidal voltage source (3V pk-pk, 100kHz centered on 0V). The given current to measure is 3Vpk-pk/500kOms= 6µA pk-pk.   


To measure the 6µA current pk-pk, do you think I can use an instrumentation amplifier to measure voltage drop across a sense resistor between the source and the 500kOms load.


I used LTSpice to simulate this using AD8421 (gain = 500, rsense = 500Ohms) and seems to give acceptable result.

I don’t have experience with instrumentation amplifier and I’m wondering if this can be implemented in practice.


Thank you in advance for your feedback on this.