Patent ID: 6978029

Claim:
A condenser microphone apparatus in which a noise output due to a high frequency signal which is radiated from a transmitting unit of a radio apparatus is reduced by attenuating the high frequency signal supplied to a signal output transmission line, the condenser microphone apparatus comprising: a movable electrode which vibrates by an acoustic vibration; a fixed electrode arranged so as to face said movable electrode; a field effect transistor that buffer-amplifies a voltage across said movable electrode and a voltage across said fixed electrode, said field effect transistor for providing the amplified voltage to the signal output transmission line; a bypass capacitor in which one end is connected to a drain terminal, acting as a signal output terminal, of said field effect transistor and the other end is connected to a source terminal, acting as a common output terminal, of said field effect transistor; and a series resistor inserted at least in one of an interval between said signal output terminal of said field effect transistor and an output terminal of the apparatus and an interval between said common output terminal of said field effect transistor and a common output terminal of the apparatus, said series resistor operating in combination with said bypass capacitor for attenuating by 90% or more the voltage or current of the high frequency signal supplied to the signal output transmission line, which high frequency signal has a frequency that is equal to or higher than 800 MHz.