How do I get a low impedance current output from this circuit?
I'm making a guess about what you're trying to do:







simulate this circuit &ndash; Schematic created using CircuitLab

You would place your circuit in place of the "Nonlinear Resistor" box, treating node VG as the ground for your circuit (VG is a virtual ground node).

VOUT will have a voltage proportional to the current through your nonlinear resistor.

Alternately, the current through R1 will be equal to the current through the nonlinear resistor, so if you want to drive a floating load, you could just place it in place of R1 (but then the output voltage might not be linearly proportional to the nonlinear resistor current).

If you want to drive a ground or supply-referenced load, you could use VOUT to drive your choice of voltage to current conversion circuit. For example, this is a common configuration: