| 摘要 |
A filter coil incorporates coils, each having the same inductance, which differ from each other in winding directions and are used for low-pass filters for eliminating carrier frequency components in BTL outputs of a class-D amplifier, which performs pulse-width modulation and amplification on input signals. A pair of coils can be arranged to adjoin together along axial directions thereof in a single package, or plural pairs of coils can be arranged to adjoin together in a single package with intervention of a magnetic shield therebetween. Alternatively, a pair of coils are wound about a single core along its axial direction with intervention of a magnetic shield therebetween. Thus, it is possible to effectively suppress inductive coupling between adjacent coils, and it is possible to realize reduction of installed areas of coils and reduction of the cost in manufacture of filter coils as well as prevention of unwanted radiation.
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