I have an dual op-amp amplifier circuit (LM833) to amplify a signal with a +-10V dual-supply rail from a 22V supply with a resistor voltage divider. The output is rectified into a 0-8V output, for which I simply require a logic output above a certain threshold (about 3V).
The problem is that the Arduino micro is powered from the same 22V supply through a switching regulator. So the ground references of the op-amp output and Arduino are at different potentials, therefore I cannot use a simple MOSFET to interface between the two circuits. Is there another way to safely connect the circuits without using a relay which would be too big and potentially too slow for the switching application.
This is a simplified schematic showing my main problem, since the arduino ground is with reference to the -10V point of the opamp.