| 摘要 |
PURPOSE:To reduce the number of parts of an amplifier block by providing a taper projecting part for positioning and fixing a fixed electrode on an insulator and dropping the fixed electrode into a metallic case together with a film ring and a gap spacer independently of the amplifier block. CONSTITUTION:A bank part 17a tapered inward is provided near the outside peripheral part of the upper end of an insulator 17, and an amplifier block 10' consists of an FET 8, the insulator 17, and a printed board 9. A fixed electrode 6 is dropped into a metallic case 2 together with a film ring 3, a diaphragm 4, and a gap spacer 5, and the amplifier block 10' is inserted thereafter. In this case, the fixed electrode 6 can be positioned and fixed because the insulator 17 is provided with the taper bank part 17a, and it is insulated from the metallic case 2 surely. The input lead of the FET 8 is interposed between the insulator 17 and the fixed electrode 6 and is made conductive by contacting or the like. |
