Differential Voltage To Current Converter (Floating Load)

This circuit supplies current to a floating load which can be connected between the output and inverting input of either op-amp. The circuit has loads in the feedback path of both operational amplifiers but these loads can be disabled by closing the switches shunting them. The saved circuit shows a load Rload1 in op amp U1 enabled and a load Rload2 in op amp U2 disabled. The output current is controlled by the difference between the voltages at the noninverting input terminals of two op amps. Through negative feedback the voltages at the inverting input terminals are equal to the input voltages. Thus, the voltage across Rset is equal to the difference between the input voltages. The current through Rset is then Irset = (Vin1 - Vin2) / Rset Since almost no current flows to the inverting input of the op amps the current to the load is equal to the current in Rset Iout = Irset = Iload So Iload = (Vin1 - Vin2) / Rset