AUDIO SIGNAL AMPLIFYING CIRCUIT AND ELECTRONIC DEVICE USING THE SAME

摘要

An audio signal amplifier capable of reducing noise in a silent state without requiring any muting transistors. In an audio signal amplifying circuit (100), a main amplifier (10) and a sub-amplifier (20) amplify an audio signal (SIG14). The sub-amplifier (20) is disposed in parallel with the main amplifier (10) and adapted to exhibit a lower drive capability than the main amplifier (10). A control part (34) controls the on/off of the main amplifier (10). The control part (34) turns off the main amplifier (10) when it is determined that an audio signal (SIG10) is in a silent state. An audio signal (SIG20), which has been amplified by the main amplifier (10) and sub-amplifier (20), is converted to an analog signal via a lowpass filter (50) and then outputted to a speaker (60).