| 摘要 |
PROBLEM TO BE SOLVED: To increase the attenuation of an adjacent channel intermediate audio carrier wave, without increasing losses in an intermediate frequency(IF) band by negatively feeding back the audio intermediate carrier wave of the adjacent IF signal of an IF signal from an output terminal through a feedback circuit to an input terminal. SOLUTION: An IF amplifier 4 has balanced output terminals 4c and 4d, one output terminal 4d is grounded in terms of high frequency and the IF amplifier 4 is made into unbalanced output. Then, a feedback circuit 5 is provided between one input terminal 4a and the other output terminal 4c. The feedback circuit 5 is composed of a resonance circuit, so that negative feedback can be loaded from the output terminal 4c of the IF amplifier 4 to the input terminal 4a at the resonance frequency (so that a signal of a phase opposite to that of an inputted IF signal can be impressed to the input terminal 4a). Therefore, when the resonance frequency of the feedback circuit 5 is matched with the frequency of the adjacent audio frequency in an IF band, audio carrier wave of a channel adjacent to a received television signal can be attenuated.
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