Patent ID: 7116171

Claim:
An operational amplifier comprising: a differential amplifier circuit of a first conduction type including a first differential pair of transistors of the first conduction type, the source of each of the transistors being connected to a first current source, and an input signal and an output signal being respectively input to the gate of each of the transistors, and a first current mirror circuit for generating drain current for each of the first differential pair of transistors; a differential amplifier circuit of a second conduction type including a second differential pair of transistors of the second conduction type, the source of each of the transistors being connected to a second current source, and the input signal and the output signal being respectively input to the gate of each of the transistors, and a second current mirror circuit for generating drain current for each of the second differential pair of transistors; a first auxiliary circuit for driving at least one of a first output node and a first inverted output node in accordance with the input signal and the output signal, the first output node representing drains of the two transistors composing the first differential pair of transistors; a second auxiliary circuit for driving at least one of a second output node and a second inverted output node in accordance with the input signal and the output signal, the second output node representing drains of the two transistors composing the second differential pair of transistors; and an output circuit including a first driver transistor of the second conduction type whose gate voltage is controlled in accordance with the voltage of the first output node, and a second driver transistor of the first conduction type whose drain is connected to the drain of the first driver transistor, and whose gate voltage is controlled in accordance with the voltage of the second output node, and outputting the voltage of the drain of the first driver transistor as the output signal, wherein the first auxiliary circuit controls the gate voltage of the first driver transistor by driving at least one of the first output node and the first inverted output node when an absolute value of a voltage between the gate and the source of the transistor composing the first differential pair of transistors and having a gate to which the input signal is input is smaller than an absolute value of a threshold voltage of the transistor, and wherein the second auxiliary circuit controls the gate voltage of the second driver transistor by driving at least one of the second output node and the second inverted output node when an absolute value of a voltage between the gate and the source of the transistor composing the second differential pair of transistors and having a gate to which the input signal is input is smaller than an absolute value of a threshold voltage of the transistor.