CAPACITANCE MEASURING CIRCUIT, CAPACITANCE MEASURING INSTRUMENT, AND MICROPHONE DEVICE

摘要

A capacitance measuring circuit 10 comprising an AC voltage generator 11, an operational amplifier 14 having a noninverted input terminal connected to a predetermined potential in this example, to the ground, an impedance converter 16, a resistor R1 12 connected between the AC voltage generator 11 and the inverted input terminal of the operational amplifier 14, a resistor R2 13 connected between the inverted output terminal of the operational amplifier 14 and the output terminal of the impedance converter 16, and an impedance element capacitor 15 connected between the output terminal of the operational amplifier 14 and the input terminal of the impedance converter 16, wherein a capacitor 17 to be measured is connected between the input terminal of the impedance converter 16 and a predetermined potential, and the capacitor measuring circuit 10 is provided in a position adjacent to the capacitor 17 to be measured.