| 摘要 |
PURPOSE:To make a response swift even if the loop gain of the level control circuit of a chrominance signal is made high, by providing a detective signal of the input burst signal to the long time constant and short time constant circuits, and controlling the level by a signal which has added those outputs. CONSTITUTION:The ACC circuit (chroma AGC circuit) is comstituted of loops of the first loop (detection circuit 2, DC amplifier 4, CR filter 5) controlling the mean value level of an input chroma signal at constant, and the second loop (detection circuit 7, CR filter 8, AC amplifier 9) following the variation of a chroma level which is comparatively fast at the time of cue and review. Even if the first loop gain is made high in order to enlarge the dynamic range of this ACC circuit, and the time constant of the loop filter is made high accompanying to said procedure, a rapid change of the chroma level variation can be compensated by the second loop. |
