Method and circuit for compensating the non-linearity of capacitors

Abstract

Capacitor voltage coefficient errors are reduced in a lossy integrator by providing oppositely oriented first and second feedback capacitors in a switched capacitor feedback circuit coupled between the output and a summing conductor connected to an inverting input of an operational amplifier. During a first clock signal, terminals of the first feedback capacitor are coupled to a reference voltage by closing first and second reset switches and the second feedback capacitor is coupled between the inverting input and the output conductor by closing first and second sampling switches. Then, during a second clock signal the terminals of the second feedback capacitor are coupled to the first reference voltage by closing third and fourth reset switches, and the second feedback capacitor is coupled between the inverting input and the output by closing third and fourth sampling switches. The opposed orientations of the first and second feedback capacitors result in time-averaging of opposite polarity voltage coefficient error charge contributions into the inverting input by the first and second feedback capacitors. In one embodiment, data-dependent flow of charge into a “quiet” reference voltage source is avoided by first coupling a capacitor to an auxiliary reference voltage source that is substantially equal to the quiet reference voltage, and later coupling the capacitor to the quiet reference voltage source.