ELECTRET CAPACITOR MICROPHONE

摘要

An electret capacitor microphone capable of removing noise in a wide range and preferably usable as a cellular telephone microphone and a vehicle engine room sensor. The microphone includes a vibration film (6) functioning as an electrode and an electret portion (E) arranged on at least one of the fixed electrodes (2, 25) arranged to oppose to the vibration film (6), thereby constituting an electro-acoustic conversion unit (M). The microphone further includes an FET (10) for impedance-converting the output of the electro-acoustic conversion unit (M). An MOS type is used for the FET (10). Moreover, a capacitor (11) and a varistor (12) are arranged in parallel between a signal line (L) and a ground portion (18) of the FET (10), and a resistor (13) is connected in series to the signal line (L).