| 摘要 |
PROBLEM TO BE SOLVED: To provide an analog mute circuit with which the effect exerted upon the arithmetic processing result by a noise level can be suppressed. SOLUTION: When a mute signalϕreaches a high level, a transfer gate 14 is made to conductive and potentials at points A and B are kept almost equal. A PWM signal L1(t) is inputted through a low-pass filter(LPF) composed of a resistor 1 and a capacitor 7 to the (-) terminal of an operational amplifier 11 and a PWM signal L2(t) is inputted through an LPF composed of a resistor 3 and a capacitor 8 to the (+) terminal of the operational amplifier 11. At the operational amplifier 11, the PWM signals L1(t) and L2(t) are added/ subtracted and the arithmetic result appears at an output point OUT.
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