OPERATIONAL AMPLIFIER

An operational amplifier is provided to control an input offset voltage by setting a potential difference between a control terminal of a first transistor and a control terminal of a second transistor. An operational amplifier includes a control signal input terminal, first and second transistors, a constant current circuit, a first resistor, and a second resistor. The control signal input terminal receives a digital control signal from an external device. The first and second transistors are a differential couple of a differential amplifying circuit. The constant current circuit provides a predetermined current to the differential couple. The first resistor has a first potential difference and is provided between the constant current circuit and the first transistor. The second resistor has a second potential difference, and is provided between the constant current circuit and the second transistor. The operational amplifier varies a resistance value ratio between the first resistor and the second resistor according to the control signal inputted to the control signal input terminal.