Patent ID: 7504880

Claim:
An amplifier circuit for level-shifting and amplifying a signal, comprising: an input terminal receiving a signal varying around a first voltage; an output terminal outputting a signal varying around a second voltage; a first terminal receiving the first voltage; s second terminal receiving the second voltage; a first resistor and a second resistor connected in series between the input terminal and the output terminal; a third resistor and a fourth resistor connected in series between the first terminal and the second terminal; an operational amplifier comprising a first differential input terminal and a second differential input terminal, the first differential input terminal being connected to a connecting node between the first resistor and the second resistor; and a first switch that selects and supplies to the second differential input terminal either the second voltage or a voltage at a connecting node between the third resistor and the fourth resistor, wherein an output of the operational amplifier is supplied to the output terminal and fed back to the first differential input terminal through the second resistor, and a ratio of a resistance of the first resistor to a resistance of the second resistor is equal to a ratio of a resistance of the third resistor to a resistance of the fourth resistor.