| 摘要 |
PROBLEM TO BE SOLVED: To provide a capacitor microphone device capable of obtaining a required output voltage, without having to use an additional amplifier, while removing the effects due to floating capacitance. SOLUTION: The capacitor microphone device has a capacitor microphone element 100, a high-input impedance amplifier 32 for amplifying the output signal of the element 100 with amplification degree G, a first voltage-dividing resistance 21, and a second voltage-dividing resistance 22. The output voltage of the amplifier 32 is divided by the first/second voltage-dividing resistances 21, 22. One terminal (a silicon substrate pad) 27 of the floating capacitance occurring in the element 100 is driven by a divided voltage. The floating capacitance, existing at the output line of the element 100, can be made very small (theoretically to zero) by a driven shield circuit, including the first/second voltage dividing resistances 21, 22. The open-end output voltage of a microphone is led to the input of the amplifier 32, without being affected by the floating capacitance so as to obtain a signal of a required output voltage, while amplifying the open end output voltage with the amplifier 32. COPYRIGHT: (C)2007,JPO&INPIT
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