| 摘要 |
PROBLEM TO BE SOLVED: To reduce pop noise of an audio amplifier, which amplifies an audio signal received from a sound source by amplifiers of a plurality of stages in order and outputs the resulting signal, without providing an offset cancel circuit on all of the plurality of amplifiers. SOLUTION: In the audio amplifier including a preamplifier serving as an electronic variable resistor and a power amplifier which amplifies the signal level of the audio signal amplified by the preamplifier up to a signal level suitable for speaker driving and outputs the audio signal, only the power amplifier is provided with the offset cancel circuit. When the audio amplifier is activated, the offset cancel circuit is placed in operation first in a state where the preamplifier is muted, and thereafter, the preamplifier is made to perform processing for amplifying and outputting the audio signal supplied from the sound source while the amplification factor is increased with time from a minimum value up to a value corresponding to reproduced sound volume set by a user. COPYRIGHT: (C)2011,JPO&INPIT
|
