| 摘要 |
PURPOSE:To prevent the generation of uneven luminance, by controlling signals with a voltage in response to a change after a prescribed time of an average level of a luminance signal, after the gain of a variable gain amplifier amplifying the luminance signal is changed for the amplification. CONSTITUTION:A limimance signal Y is applied to LPFs 10, 11 of an integration circuit constitution having a sufficiently longer time constant in comparison with 1H via analog switches 8 and 9. Outputs of both the LPFs are applied to input terminals of a differential amplifier 12 respectively, the outut of the amplifier 12 is applied to one input terminal of a changeover switch and a constant voltage E is applied to another terminal and a circuit 13 is controlled with an FF14. Every time a horizontal synchronizing signal comes, the Q and Q' of the FF14 are made opposite in phase and the switches 8 and 9 are turned on at each 1H. Thus, the signal Y is applied to the LPFs 10 and 11 alternately at each 1H and a voltage in response to the average level of the signal Y is outputted. |
