Hello all,
I have a question regarding leakage measurement circuits (...if there is such a thing):
Are there typical circuits for measuring leakage current ? The ranges which I want to measure are 0-100pA and 0-1nA. I want to digitize the leakage current value in order to store it (digitally), so at the I would be needing an ADC component as well.
What initially came to mind was to place a [200k or 2M] resistor in the path to the ground (of the DUT). The voltage generated at the resitor's node (the other resistor node is gnd) will have a granularity of [200nV or 2uV, depending the resitor value of [200k or 2M]] per 1pA of leakage current. This voltage can build up to [200uV or 2mV] for a
1nA maximum leakage current. Hence the DUT should operate ok; its ground node can only rise up to a max of 2mV. Now I would need to amplify this voltage. The problem is that if I amplify this voltage trough a typical (1+R2/R1) opamp architecture is that it probably would not work well because of the nearness to the bottom power rail of the opamp. Not to mention of the noise that has to be filtered out prior to amplifying this low voltage level. (...Afterwards, when we have obtained an acceptable output voltage range (~1V), we digitize this voltage with an ADC...)
Please advise.
-Roger