| 摘要 |
PURPOSE:To decrease a terminal pin by providing first and second power amplifiers, respective input terminals and a polarity inverting circuit, changing the direct current level of a second input terminal and using it for an action mode switching control terminal and a signal input terminal. CONSTITUTION:An input terminal 1 is connected to input amplifiers 3, 4 and 5 and an input terminal 2 is connected to an input amplifier 6 and a switch control circuit 20. A switch 7 supplies one side output of the amplifiers 3 and 4 to the non-inverting input terminal of a power amplifier 10 in accordance with the control signal of the control circuit 20. A switch 8 guides or turns off the output of the amplifier 5 to the inverting input terminal of a power amplifier 11 in accordance with the control signal of the control circuit. A switch 9 also guides or turns off the output of the amplifier 5 to the non- inverting input terminal of the power amplifier 11 with the signal of the control circuit 20. By the constitution, the second input terminal comes to be an action mode switching control terminal by the change of the direct current level and the number of terminal pins is decreased.
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