Patent ID: 6919766

Claim:
An operational amplifier circuit comprising: a constant current source circuit that includes a first transistor and a first resistor element connected between the gate and the source of the first transistor, wherein the constant current source circuit makes a first current flowing across the first resistor element equal to a first drain current flowing in the first transistor, wherein the constant current source circuit includes a second transistor, the source of which is connected to the first resistor element and the gate of which is connected to the drain of the first transistor, and a current mirror circuit including a third transistor, the drain of which is connected to the drain of the first transistor, and a fourth transistor, the drain of which is connected to the drain of the second transistor; an output stage circuit including first and second output transistors connected to an output terminal of the operational amplifier circuit, the second output transistor having the same polarity as that of the first transistor, the output stage circuit including a second resistor element connected between the source and the gate of the second output transistor; and a differential input circuit including first and second input transistors for respectively receiving first and second input signals and a current mirror circuit that includes fifth and sixth transistors respectively connected to the first and second input transistors.