AUDIO SIGNAL AMPLIFIER CIRCUIT, INVERTING AMPLIFIER, AND ELECTRONIC APPARATUS USING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide an audio signal amplifier circuit suppressing noise. SOLUTION: An inverting amplifier 10 for driving a headphone 6 through an output capacitor C2 includes: an operation amplifier 14; an input resistance Ri having a first terminal for receiving an audio signal VI to be amplified and a second terminal connected to an inverting input terminal (-) of the operation amplifier 14; and a feedback resistance Rfb having a first terminal connected to an inverting input terminal (+) of the operation amplifier 14 and a second terminal connected to an output terminal of the operation amplifier 14. A reference voltage source 20 generates a bias voltage Vb and supplies it to a non-inverting input terminal (+) of the operation amplifier 14. A discharge path 12 includes a discharge resistance Rdis and a first switch SW1 disposed in series between an output terminal of the reference voltage source 20 and a fixed voltage terminal. A second switch SW2 is disposed between the output terminal of the operation amplifier 14 and a node on the discharge path 12 with a potential higher than the discharge resistance Rdis. COPYRIGHT: (C)2011,JPO&INPIT