High DC Voltage Current Sensing

LTC6101 op-amp can be used to build High voltage current monitoring/sensing. This circuit can senses current in 500 volts system. Here is the schematic diagram of the circuit:

To hold off the voltage, two external Mosfets is added to the circuit. It will allow to connect LTC6101 to very high potentials and measure the current flow.  At Rsense, the output current from the op-amp is proportional to the sensed voltage. It flows through M1 and create a ground referenced output voltage. [Schematic diagram source: Linear Technology Application Notes]