| 摘要 |
PURPOSE:To correct a part in which color saturation is increased unnaturally by applying gain control to a color difference signal subject to gain control through a voltage variable amplifier whose gain is controlled by a luminance signal before gamma correction. CONSTITUTION:The luminance signal before gamma correction inputted to a gain control circuit 15 is used as a signal controlling gain control circuits GCA 18, 19. As the concrete circuit of the GCA18, 19 controlling the amplitude of the color difference signal by the luminance signal, in such a way, voltages VB1 and VB2 are applied respectively to the bases of a couple of transistors being components of a differential amplifier shown in the fig. The gain control characteristic is the S-shape characteristic and a control input DELTAVB=VB1-VB2 is applied. When the level of the luminance signal is low, a maximum point of the control input DELTAVB having a small gain change is used. When the level of the luminance signal is high, the luminance signal is applied while being offset (20) by bringing the level to a point around DELTAVB=0 having much gain change.
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