I'm trying to build a high voltage capacitor leakage tester with current limiting feature, below circuit is the simplified and raw idea:
Problem with that circuit is the current passing through the OA1 resistors, that's causing error, discharging the capacitor and essentially makes this circuit useless.
I can't buffer such high voltage and can't increase the resistor value too high because then I have to deal with noise...
- How can I buffer the input voltages of OA1 differential amplifier?
The current is being measured in differential mode but I didn't include that in the schematic.
I want to test capacitors leakage and diodes (LED, zener), that's why I need to measure the voltage too.
Maximum current is 100 mA.
Input voltage is selectable from 10 V to 400 V in 12 steps.