| 摘要 |
PURPOSE:To simplify the construction of an external circuit and to miniaturize an FM receiver, by connecting one end of a capacitor to an output extraction section of an FM system IC and providing an operational amplifier grounding the capacitor side in terms of AC for the other end. CONSTITUTION:One end of a coupling capacitor 24 is connected to an extraction section of an output of an AFC tuning meter circuit 14 of the FM system IC1 and the operational amplifier 26 grounding the capacitor side 24 in terms of AC is connected to the other end of the capacitor 24. A muting drive section 5 is connected to an output side of the amplifier 26 via an HPF3 and a noise detection circuit 4 determining a noise level. The output side of the amplifier 26 is designated as the 2nd demodulation output terminal to a terminal of a muting drive section 15 of the IC1 and the muting is performed when the noise in the demodulated output is a prescribed level or over. The constitution of the external circuit to the IC1 is simplified and the FM receiver is miniaturized. |
