1. A circuit for reversible trimming a matching resistor to a reference resistor wherein the matching resistor material comprises a programmable resistance material with a mono-polarity switchable property, the circuit comprising a resistor bridge network comprising a reference resistor and a matching resistor, the resistor bridge network comparing the resistance states of the reference resistor and the matching resistor and generating a comparing signal indicative of the difference between the reference resistor and the matching resistor; and a pulse feedback circuit, the feedback circuit coupled to the resistor bridge network and providing a mono-polarity electrical pulse signal corresponding to the comparing signal to modify the resistance of the matching resistor toward that of the reference resistor.