Patent ID: 6792121
Filing Date: 2004-09-14
Classification: H03F

Abstract:
An audio signal amplifier circuit formed as an IC and having an input stage including a differential amplifier and an output stage including a single-ended power amplifier circuit, said audio signal amplifier circuit comprising: an external output terminal of said IC connected to an output line of said single-ended power amplifier circuit; a first resistor connected between a certain terminal of said IC other than said external output terminal and a feedback input of said differential amplifier circuit; a first capacitor connected between said external output terminal and a loud speaker; a second capacitor between said certain terminal of said IC and a wiring line between said external output terminal and said loud speaker; a filter circuit provided on a signal input side of said differential amplifier circuit and including a second resistor and a third capacitor for attenuating signal components having frequencies in a middle and high frequency ranges; and voltage follower means provided between said input stage and said output stage, wherein said first capacitor is a small capacitor having a capacitance value in the order of 30 &mgr;F or smaller and an attenuation characteristics of said first capacitor and an impedance of said loud speaker in a low frequency range is compensated for by a relative amount of increase of amplification gain in the low frequency range determined by a time constant of said second capacitor and said first resistor and a time constant of said third capacitor and said second resistor.