In one embodiment, an apparatus includes a first capacitor system and a second capacitor system. Each capacitor system comprises one or more engaged capacitors from respective pluralities of selectively engagable capacitors. The first capacitor system and second capacitor system are respectively selectively coupled to a first reference voltage and a second reference voltage. The apparatus further includes a 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 apparatus further includes 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 is configured to bias the differential amplifier to the first voltage.