Operational amplifier and operation method thereof

The invention discloses an operational amplifier, which relates to the field of integrated circuits and comprises a first input end and a second input end, inputting a signal; receiving two input signals using a first input and a second input; a dual-input amplifier; receiving an input signal from the first and second input terminals; a zeroing amplifier; a dual-mode operational amplifier is used for generating a bias voltage to compensate for the offset voltage generated by the zeroing amplifier and the main amplifier, the dual-mode operational amplifier provides both a differential mode and a single-ended mode, compared with two independent amplifiers, the dual-mode operational amplifier needs fewer chip areas, the manufacturing cost is reduced, and the dual-mode operational amplifier has the advantages that the dual-mode operational amplifier is simple in structure and low in cost. The two-stage common-mode feedback circuit for detecting the voltage of each stage of amplifier is adopted, so that the common