Temperature characteristics of electret condenser microphones

A microphone should be robust when it is used for the mobile equipments. Generally in diaphragm electret type, as the temperature characteristic of diaphragm stiffness and gain characteristic of FET is opposite. These properties make the temperature characteristics of the sensitivity compensated to be almost flat. On the other hand, as fixed electrode electret type using PET diaphragm which has the same temperature coefficient as FET, consequently it is difficult to compensate the temperature characteristics. It is insufficient to say that still it is robust to temperature. In order to improve the temperature characteristic, an evaluation method about the temperature dependence of acoustic characteristics of electret condenser microphone is proposed. This report refers to the temperature dependence of the dominant parameter which the sensitivity of the microphone is being determined, and reported about the design method of the microphone that a temperature characteristic is stable. Finally, the silicone of the inorganic material is applied to the diaphragm and source follower circuit is effective about the high temperature 80 degrees C in impedance converter The possibility of electret condenser microphone which has a flat temperature characteristic was proposed.