| 摘要 |
PROBLEM TO BE SOLVED: To provide an output filter for a digital power amplifier that limits a frequency band of a signal outputted from the digital power amplifier and prevents unnecessary electromagnetic waves from being emitted and to provide the digital power amplifier. SOLUTION: Windings 31, 32 of the output filter 13 for the digital power amplifier are wound on a common core in opposite directions to each other to form normal mode coils 33, 34 and wound on the core in the same directions to each other to form a common mode coil 35. The normal mode coils 33, 34 pass through only components with a required frequency band from signals outputted from the digital power amplifier 12 to eliminate components with an undesired frequency band. Furthermore, the common mode coil 35 cancels the common mode component in a differential signal outputted from a noninverting output terminal 23 and an inverting output terminal 24 of the digital power amplifier 12 to eliminate the noise component.
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