PURPOSE: To cancel noises at the time of weak electric field and to improve an S/N by detecting a video signal level by using AGC voltage and controlling the high-pass response of a signal line by the detected output.
CONSTITUTION: In a noise canceler circuit 20, a signal Sc from an amplifier 14 is taken out in the output terminal through the non-inversion input terminal of an operational amplifier 21, and at the same time, a by-pass filter 22 is constituted at the output terminal of the amplifier 14, and a signal obtained at the junction is supplied to the inversion input terminal of an amplifier 21 through a variable gain amplifier 23. AGC voltage Sa is supplied to the inversion input terminal of an operational amplifier 24 for voltage comparison. At the same time, reference voltage of E1 is supplied to the non-inversion input terminal of the amplifier 24, and output voltage Sg of the amplifier 24 is supplied to the amplifier 23 as a controlling signal of gain.
SAKAMOTO TETSUO
FUKUSHIMA SHINYA
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