Patent ID: 7423698

Claim:
An amplifier for amplifying an input signal, wherein an amplified signal which varies with a ground voltage as a center voltage is obtained at an output of the amplifier using a positive power supply and a negative power supply, wherein the negative power supply is generated based on the positive power supply, and wherein the negative power supply comprises: a charging constant current circuit which outputs a constant current from the positive power supply; a discharging constant current circuit which outputs a constant current to a ground power supply; a first switch which selects one of the charging constant current circuit and the discharging constant current circuit; a capacitor having a first terminal connected to the first switch and which is charged and discharged; and a second switch which selectively connects a second terminal of the capacitor to ground or to an output terminal, and the second terminal of the capacitor is connected to ground by the second switch when the charging constant current circuit is selected by the first switch and the second terminal of the capacitor is connected to the output terminal by the second switch when the discharging constant current circuit is selected by the first switch, so that an output of a charge pump circuit for obtaining an output voltage which is lower than the ground by a voltage corresponding to the positive power supply is obtained at the output terminal.