An apparatus includes an input port, an output port, a resistor, and a current amplifier. The current amplifier includes an input circuit and an output circuit. The resistor is coupled to the input port. The input circuit is coupled to the resistor and the output circuit. The output circuit is coupled to the output port, the input circuit and the output circuit. The input circuit and output circuit have substantially identical topologies. A method includes receiving an input voltage signal, converting the input voltage signal to a current signal, and processing the current signal to form a feedback signal and an output current signal that is a substantially linear representation of the input voltage signal.