| 摘要 |
PURPOSE:To decrease a noise and to hold a circuit highly stably by making the constant voltage of a constant voltage circuit into an operating voltage, supplying it to a capacitor microphone unit and impressing it to an FET as a bias voltage. CONSTITUTION:A constant voltage outputted from a constant voltage circuit 10 is impressed through a high resistance 11 as one edge of a capacitor microphone unit (CMU) 12 and the bias voltage of an FET 13. The CMU 12 outputs the signal of a electrostatic capacity change to the gate terminal of the FET 13 corresponding to the sound wave to be inputted, and to the source terminal of the FET 13, the impedance-converted electric signal is outputted. The electric signal is converted by a transformer 16 and outputted from an output terminal 17. Thus, since a coupling capacitor is not needed and one high resistance is sufficient, the noise can be suppressed and the stable output can be obtained. |
