| 摘要 |
PROBLEM TO BE SOLVED: To provide a speaker protecting circuit capable of suppressing an offset current of a speaker generated owing to voltage abnormality of a reference bias terminal with relatively simple constitution. SOLUTION: The speaker protecting circuit includes a voltage comparator 30 which compares a voltage at the reference bias terminal 5 of an amplifying circuit constituting a BTL amplification device with a previously set threshold voltage V1; and first and second switches 32 and 33 which switch to supply or cut off currents to two power amplifying circuits 15 and 16, and turns off at least one of the first and second switches 32 and 33 according to the output level of the voltage comparator 30, when the voltage at the reference bias terminal 5 is lower than the threshold voltage V1 to cut off current supply to the power amplifying circuits 15 and 16, thereby stopping a speaker 21 from being driven by the power amplifying circuits 15 and 16. COPYRIGHT: (C)2007,JPO&INPIT
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