Patent ID: 7342390

Claim:
A reference voltage generation circuit comprising: a first current source and a first transistor connected in series between a first power-supply line and a second power-supply line; a second current source, a first resistor, and a second transistor connected in series between said first power-supply line and said second power-supply line; a third current source, a first switch, and a first variable resistor connected in series between said first power-supply line and said second power-supply line; a first operational amplifier circuit having inputs connected to a first resistance node and an emitter of said first transistor respectively, and an output connected to control terminals of said first, second, and third current sources, thereby equating a voltage of the first resistance node and a voltage of the emitter of said first transistor, the first resistance node being a connection node of said second current source and said first resistor; a fourth current source and a second variable resistor connected in series between said first power-supply line and said second power-supply line; a fifth current source and a second switch connected in series between an output node and said first power-supply line, the output node being a connection node of said first switch and said first variable resistor; and a second operational amplifier having inputs connected to a second resistance node and the emitter of said first transistor respectively, and an output connected to control terminals of said fourth and fifth current sources, thereby equating a voltage of the second resistance node and the voltage of the emitter of said first transistor, the second resistance node being a connection node of said fourth current source and said second variable resistor, wherein: said first transistor has a base and a collector connected to said second power-supply line; said second transistor has a base and a collector connected to said second power-supply line and operates with a current density different from a current density of said first transistor; said first switch is on in a first operation mode and a third operation mode and is off in a second operation mode; and said second switch is on in the first operation mode and the second operation mode and is off in the third operation mode.