| 摘要 |
PROBLEM TO BE SOLVED: To provide an AM and FM broadcast receiving circuit that is not large in the total size of a circuit and can be reduced in size, because AM signal reception and FM signal reception are switched using a variable attenuation circuit 5 for FM signal that can also be used as an automatic control circuit of an FM broadcast signal level. SOLUTION: The receiving circuit is provided with an FM tuner circuit 7 to form a demodulation signal by processing the FM broadcast signal received by a common antenna 1, an AM tuner circuit 4 to form a demodulation signal by processing the AM broadcast signal received by the common antenna 1, a signal attenuation circuit 5 connected at the preceding stage side of the FM tuner circuit 7, and a control circuit 8 for controlling the signal attenuation of the signal attenuating circuit 5 and switching the operating or non-operating condition of the FM tuner circuit 7 or AM tuner circuit 4. The control circuit 8 automatically controls, when the FM tuner circuit 7 is operated, the signal attenuation of the signal attenuating circuit 5 to set the signal intensity of the FM broadcast signal inputted to the FM tuner circuit 7 to predetermined intensity and also controls the signal attenuation of the signal attenuating circuit 5 to the maximum attenuation degree when the AM tuner circuit 4 is operated. COPYRIGHT: (C)2008,JPO&INPIT
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