Patent ID: 8854137

Claim:
An operational amplifier circuit, the operational amplifier circuit comprising: a differential amplifier of a cascade structure, for amplifying a difference between two input signals to output an anode output voltage and a cathode output voltage; and a switched-capacitor type Common-Mode FeedBack (CMFB) circuit for averaging the anode output voltage and the cathode output voltage of the differential amplifier, for comparing the average voltage with a reference voltage to generate a feedback signal based on a result of the comparison, and for providing the feedback signal to the differential amplifier, wherein the switched-capacitor CMFB circuit charges, in a first time period, a second capacitor, connected between an ideal common output voltage and an ideal input bias voltage, and a first capacitor, connected between an output voltage of the differential operational amplifier and a feedback output voltage, and discharges the second capacitor to the first capacitor in a second time period.