I want to measure a differential voltage in which the common mode voltage is higher than my circuit's supply voltage.
The measuring circuit and the circuit being measured share a common ground.
I'm designing a multi-channel volt- and amp-meter, this is the reason. I want to have a low power supply voltage.
Voltage measuring poses no problems. The tricky part is current measurement; although the (differential) voltages are quite small, the common mode voltage may not be.
I played a bit with AMPOPs but they seem to need a supply voltage higher than the common mode one... I need some ideas.