| 摘要 |
PURPOSE:To reduce variation in oscillation frequency with a source voltage by flowing a current to one diode during switching and also applying a reverse bias to the other diode in an off state through a coil at the same time. CONSTITUTION:A band changeover switch 21 is switched to the stage of continuity between terminals (a) and (c) for FM broadcast reception. Consequently, a current flows through a resistance 7, choke coil 4, a changeover diode 2, an FM oscillation coil 12, and a resistance 18 in order. Then, a voltage divided by resistances 6 and 7 is applied as a reverse bias to a changeover diode 14 through a choke coil 1. Then, the switch 21 is switched to the state of continuously between terminals (a) and (b) for TV broadcast reception. Consequently, the current flows through a resistance 19, a TV oscillation coil 17, a diode 14, a choke coil 1, and a resistance 6 in order. A voltage divided by resistances 18 and 19 is applied as a reverse bias to the diode 2 through the coil 12. Consequently, variation in the capacity between diode terminals becomes small and variation in oscillation frequency is reduced.
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