| 摘要 |
PURPOSE:To eliminate the difference in video frequency characteristics between reception channels by providing a video amplifier circuit changing the video frequency characteristic and extracting a burst signal from a received video signal to adjust the variable amount of an amplifier circuit in response to the amplitude. CONSTITUTION:A composite video signal (a) is inputted to a synchronizing separator circuit 1 of a video frequency automatic correcting circuit, a pedestal clamp circuit 4 and a video signal amplifier circuit 9. The circuit 1 extracts only a synchronizing signal portion, a square wave (b) is delayed by a delay circuit 2 and a square wave (c) is inputted to an inverse circuit 3 and the circuit 4. The square wave (c) is synchronized with a back porch of the signal (a) and used as a driving square wave for the circuit 4 and a burst extraction circuit 5, the circuit 5 extracts only the burst and a signal (e) applying DC clamp to the back porch is inputted to a peak detection circuit 7. A DC voltage (f) representing the peak detection characteristic from the circuit 7 is processed by a DC voltage correcting circuit 8, the variable amount of an amplifier circuit 9 is adjusted in response to the level of a voltage (g) to make the difference in the video frequency characteristics between reception channels uniform. |
