Patent ID: 7304458

Claim:
A regulator circuit comprising: a first transistor; a first resistor and a second resistor connected in series with the first transistor; a first operational amplifier comprising a first differential input terminal and a second differential input terminal, a reference voltage being applied to the first differential input terminal, a voltage at a node between the first and second resistors being applied to the second differential input terminal, and an output of the first operational amplifier being applied to a gate of the first transistor; a second transistor connected in series with the first and second resistors; a second operational amplifier comprising a third differential input terminal and a fourth differential input terminal, the reference voltage being applied to the third differential input terminal, the voltage at the node between the first and second resistors being applied to the fourth differential input terminal, and an output of the second operational amplifier being applied to a gate of the second transistor; and a switching circuit making the first operational amplifier to operate and the second operational amplifier not to operate in a first mode and making the first operational amplifier not to operate and the second operational amplifier to operate in a second mode, wherein a current driving capability of the second operational amplifier is smaller than a current driving capability of the first operational amplifier.