| 摘要 |
PURPOSE:To set independently the response of automatic gain control AGC between a synchronizing signal and a peak signal by selecting an output of a level comparator means when no peak is detected and selecting an output of the peak detection means when detected by one vertical scanning period so as to obtain a gain control signal. CONSTITUTION:A selected output of a switch 25 is used as a gain control signal through a filter 27 and given to a gain adjustment circuit 21, where the gain is adjusted. In the vertical scanning period next to the vertical scanning period where the discrimination output representing the presence of the peak detection output, the time constant of the filter 27 is decided by charge/discharge of a peak detection circuit 24. Conversely, in the field next to the field where the discrimination output without the peak detection output is obtained, the time constant of the filter 27 depends on charge/discharge of the level comparison circuit 23. Thus, the response is set independently of the synchronizing AGC and the peak AGC.
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