| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a capacitor microphone apparatus which is hardly affected by external noise. Ž<P>SOLUTION: A bias voltage +Vcc is applied between a power supply terminal 30 and a ground. A bias resistor 32, a microphone element 34 and a bias resistor 36 are connected in series between the power supply terminal 30 and the ground. Resistance values of the bias resistors 32, 36 are each set to high resistance values from 100 GΩ to 100 TΩ. Signals of a back plate 34a and a diaphragm 34b of the microphone element 34 are passed through signal lines 45, 46 and impedance-converted by impedance converters 38, 40, respectively. Output signals of the impedance converters 38, 40 are input through a balanced signal line 42 to an arithmetic circuit 44. The arithmetic circuit 44 adds both the signals after inverting one of the signals. A microphone signal is output from the arithmetic circuit 44. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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