| 摘要 |
PROBLEM TO BE SOLVED: To constitute an audio amplifier which automatically keeps a sound volume level fixed approximately even when the impedance characteristics of a load connected to a speaker output changes due to the exchange of a speaker or the like. SOLUTION: An input voltage detection part 10 detects the voltage of an input signal Vin, and an output power detection part 30 detects output power from an amplifier part 20 to a speaker 100. A gain control part 40 controls the gain of the amplifier part 20 in accordance with the extent of operation of an external operation part 50 so that the ratio of the output power to the voltage of the input signal Vin is approximately fixed as far as the extent of operation of the external operation part 50 is fixed. COPYRIGHT: (C)2005,JPO&NCIPI
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