| 摘要 |
PURPOSE:To attain sound reproduction without losing the sound quality by providing on integration circuit receiving a high frequency component level rectified by a level detector and smoothing the result, a low pass filter and a variable resistive element so as to eliminate undesired high frequency components depending on the content of broadcast. CONSTITUTION:The audio signal is rectified by a level detector 5 through an HPF 4 extracting only the high frequency component of the audio signal, the high frequency component level is converted into a DC voltage by an integration circuit 6 and the result is given to a gate of the variable resistive element FET 7 as a control voltage. The drain-source resistance RDS with respect to the gate voltage from the variable resistive element FET 7 is larger toward lower negative voltage and shots a resistance change in response to the level of the high frequency component. Thus, the variable resistive element FET 7 is connected between the capacitor 3 of a low pass filter LPF 1 comprising the resistor 2 and the capacitor 3, and ground. Thus, the high frequency noise is suppressed and the television audio signal with excellent S/N is reproduced.
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