SILICON MEMBRANE CONDENSER MICROPHONE WITH INTEGRATED FIELD-EFFECT TRANSISTOR

Silicon condenser microphones with integrated field-effect transistor and three different membrane structures were designed and built. Micro phone membranes, which are suspended at four bending beams only and ot herwise free to oscillate when exposed to sound pressure, show in the frequency range below 10 kHz a very high sensitivity of up to 38 mV/Pa . They are by a factor of four higher in sensitivity as compared with the conventional closed-plate membrane of the same membrane area and m embrane thickness averaged over this frequency range.