Patent ID: 7199654

Claim:
An amplifier circuit operating in at least a first stage and a second stage, comprising: an operational amplifier having two or more signal inputs and one or more signal outputs, the operational amplifier having feedback from at least one of the signal outputs to at least one of the signal inputs; first switching circuitry switching among multiple elements providing input for the operational amplifier, the first switching circuitry providing at least a first signal to one of the signal inputs of the operational amplifier for the first stage of the amplifier circuit and a second signal to one of the signal inputs of the operational amplifier for the second stage of the amplifier circuit; second switching circuitry switching among multiple elements providing feedback for the operational amplifier, the second switching circuitry providing at least a first capacitive value as the feedback of the operational amplifier for the first stage of the amplifier circuit and a second capacitive value as the feedback of the operational amplifier for the second stage of the amplifier circuit; and third switching circuitry substantially reducing parasitic charge at one or more of the signal inputs of the operational amplifier.