| 摘要 |
<P>PROBLEM TO BE SOLVED: To secure a rated output while improving S/N ratio at a low volume position in a sound output device. Ž<P>SOLUTION: Transistors 41, 42 which operate according to control signals output from a control portion 7 are provided between the control portion 7 and a digital amplifier 40. Responding to the operation of the transistors 41, 42, control signals input to a first gain input terminal 51 and a second gain input terminal 52 of a digital amplifier 40 vary high or low respectively. The digital amplifier 40 changes a gain value according to the control signals input to the first gain input terminal 51 and the second gain input terminal 52. When the output of a speaker is small, the gain value of the digital amplifier 40 is set small, when the output of a speaker is large, the gain value of the digital amplifier 40 is set large. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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