Patent ID: 7342443

Claim:
An operational amplifier for generating an output voltage by amplifying an input voltage, the operational amplifier comprising; a first capacitor; a first operational amplification unit connected to the first capacitor and having a first offset voltage, the first operational amplification unit accumulating charge corresponding to the first offset voltage in the first capacitor and alternately performing a canceling operation, for canceling the first offset voltage with the charge accumulated in the first capacitor, and a non-canceling operation, for generating a first output voltage by amplifying the input voltage; a second capacitor; a second operational amplification unit connected to the second capacitor, having substantially the same electrical characteristic as the first operational amplification unit, and having a second offset voltage, the second operational amplification unit accumulating charge corresponding to the second offset voltage in the second capacitor and alternately performing a canceling operation, for canceling the second offset voltage with the charge accumulated in the second capacitor, and a non-canceling operation, for generating a second output voltage by amplifying the input voltage; and an output selection circuit, connected to the first and second operational amplification units, for alternately selecting the first output voltage and the second output voltage as the output voltage of the operational amplifier; wherein the second operational amplification unit performs the non-canceling operation when the first operational amplification unit is performing the canceling operation, and the second operational amplification unit performs the canceling operation when the first operational amplification unit is performing the non-canceling operation.