Patent ID: 8421666

Claim:
An apparatus comprising: a first capacitor system having a first variable capacitance, the first variable capacitance based, at least in part, upon a number of engaged capacitors of a first plurality of selectively engagable capacitors, the first capacitor system selectively coupled to a first reference voltage; a second capacitor system having a second variable capacitance, the second variable capacitance based, at least in part, upon a number of engaged capacitors of a second plurality of selectively engagable capacitors, the second capacitor system selectively coupled to a second reference voltage; a switch coupled to the first capacitor system and the second capacitor system, the switch configured to transfer charge between the first capacitor system and the second capacitor system when the switch is closed such that the first capacitor system and the second capacitor system each store the same first voltage, the first voltage less than the first reference voltage; and a node coupled to the first capacitor system, the second capacitor system, and a first input of a differential amplifier of an analog to digital converter, the node configured to bias the differential amplifier to the first voltage.