A circuit including an amplifier. The circuit includes N capacitances that include first ends and second ends. The first ends communicate with an input of the amplifier. A first switch is configured to selectively connect the input of the amplifier to a reference potential during a first phase. N switches are configured to connect each of the second ends of the N capacitances to a voltage input, the reference potential and a voltage reference and selectively connect each of the second ends of the N capacitances to one of a voltage input, the reference potential and a voltage reference during a second phase. The first and second phases are non-overlapping.