| 摘要 |
PROBLEM TO BE SOLVED: To supply a mute signal without using any exclusive terminal to a bias circuit which supplies reference currents to all blocks. SOLUTION: This mute circuit is provided with a switching transistor 20 whose collector/emitter electrode path is connected between a bias circuit 12 and a ground, and whose base is connected to a reference voltage terminal, and when a reference voltage to be supplied to the reference voltage terminal 16 is not more than the operating voltage VBE of the switching transistor 20, the switching transistor 20 is turned off, and the bias circuit 12 is made inoperable so that bias currents to the all blocks 13 can be interrupted. Thus, it is possible to realize a mute operation.
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