| 摘要 |
PURPOSE:To improve performance such as contrast and color saturation and to prevent a defective in reproduction hue by providing a circuit which detects the amplitude of an index signal before amplitude limitation and a circuit which controls amplitudes of chrominance components, and reduding an amplitude for a driving signal for an index tube when the amplitude of the index signal is smaller than a specific value. CONSTITUTION:The circuit which detects amplitude information on the index signal lowers the output voltage at a terminal 30 when the amplitude of the index signal is large and raises the output voltage at the terminal 30 when the amplitude of the index signal is smaller. Then, a gain control circuit 7 constitutes a full balance type differential amplifier on the whole; and an output signal having a large amplitudde is obtained at an output terminal 70 when the voltage at a terminal 69 drops and the amplitude of the output signal decreases when the voltage at the terminal 69 rises. Those index signal amplitude detecting circuit 6 and gain control circuit 7 are used to decrease the amplitudes of chrominance components for driving the index tube.
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