| 摘要 |
PROBLEM TO BE SOLVED: To obtain a ferrite toroidal coil which can be assembled easily, manufactured at low cost, and make the characteristics of a filter easily changeable or adjustable, without damaging a substrate. SOLUTION: A case 10, which has a cylindrical external shape and a doughnut-like internal cavity, can be divided into a case bottom plate 11 and a case cap 12 so that the whole internal cavity can be opened and made of an insulating material, is prepared. Terminals 20a and 20b are formed on the external surface of the case 10 and pattern wiring 30a and 30b both ends of which are respectively connected to the terminals 20a and 20b and which are spirally wound along the internal surface of the cavity, and the wirings 30a and 30b are connected to each other, when the case cap 12 is put on the case bottom plate 11. A doughnut-like ferrite core 40 is housed in the internal cavity of the case 10 for carrying the terminals 20a and 20b and the pattern wiring 30a and 30b.
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