| 摘要 |
PURPOSE:To keep the relative ratio of both chrominance carrier signals constant at a synthesis video signal by generating a DC control voltage based on a burst signal extracted from the video signal and using the said voltage so as to control the gain of an amplifier of a carrier signal attended with the level fluctuation of the burst. CONSTITUTION:A burst detecting circuit 2 detects the burst signal, which is amplified and fed to a DC control voltage generating circuit 4. The signal is conducted at the positive half cycle of the burst through a diode 4a in the circuit 4, charged into a capacitor 4b so as to form a control voltage. In order to control sufficiently the gain of the chrominance carrier signal by the burst level, the amplified control voltage is formed by a DC amplifier 4c. The level of the chrominance carrier signal of an encoder is amplified in response to the quantity of the burst signal of the video signal by applying the said voltage to an amplifier 5 having a DC voltage control terminal to keep the relative ratio of the chrominance carrier signal level of the video signal constant.
|
