Patent ID: 7982537

Claim:
An operational amplifier, comprising: a pair of level shift circuits that convert levels of a pair of differential input signals and output the level converted differential signals; and a pair of differential amplifiers each having a pair of inputs each connected to a differential output of one of the level shift circuits; and an output stage having a pair of inputs each connected to a corresponding output of the pair of differential amplifiers, wherein the level shift circuits and the differential amplifiers cooperate to detect a level difference between the pair of differential input signals and to control a driving ability with respect to the output stage in accordance with the detected level difference, wherein the pair of level shift circuits include a first level shift circuit which has an input connected to one differential input signal, and which outputs a first potential voltage by adding a voltage to said differential input signal and a second potential voltage higher than the first potential voltage, a second level shift circuit which has an input connected to another differential input signal, and which outputs a third potential voltage by adding a voltage to said another differential input signal and a fourth potential voltage higher than the third potential voltage, wherein the differential amplifier includes a first conductivity type transistor differential pair which have respective inputs connected to an output of the second potential voltage and to an output of the fourth potential voltage and having first ends connected to each other at a first connection, a second conductivity type transistor differential pair which have respective inputs connected to an output of the first potential voltage and to an output of the third potential voltage and having first ends connected to each other at a second connection, a first current voltage conversion circuit connected to a second end of each of the first conductivity type transistor differential pair, a second current voltage conversion circuit connected to a second end of each of the second conductivity type transistor differential pair, and a driving current control circuit which causes a voltage drop by a current flowing in the first conductivity type transistor differential pair and in the second conductivity type transistor differential pair, wherein the first current voltage conversion circuit is connected to a first power supply, wherein the second current voltage conversion circuit is connected to a second power supply having a lower potential than the first power supply, and wherein the first connection and the second connection are connected in series with the first power supply and the second power supply through the driving current control circuit.