| 摘要 |
PROBLEM TO BE SOLVED: To provide a manufacturing method of an electret capacitor microphone by which the variation of sensitivity characteristics can be sufficiently suppressed small. SOLUTION: A target charge voltage Vc of a back electrode plate suited to obtain a predetermined target sensitivity is preset in accordance with a drain saturation current IDSS of a junction field effect transistor and a lowest resonant frequency F0 of a vibrating film. In that case, the drain saturation current IDSS is classified into a plurality of ranks (1)-(6). The drain saturation current IDSS of the junction field effect transistor and the lowest resonant frequency F0 of the vibrating film are then actually measured and polarizing processing is applied to the back electrode plate with the target charge voltage Vc corresponding to these two measured values. Thus, in comparison with the conventional case of adopting a selection method or a control method paying attention only to the charge voltage of the back electrode plate, the variation in sensitivity characteristics is remarkably suppressed small. COPYRIGHT: (C)2004,JPO&NCIPI
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