DC restoration for video cameras - provides reference signal for black level clamp from blanking pulse fed to storage capacitor and buffer amplitude

摘要

The DC restoration circuit for television cameras with high scanning frequencies e.g. 875 lines reduces high voltage peaks in the line blanking period. The video camera (1) is supplied with line and frame scan pulses from a central control unit (IZ) which also provides the blanking pulses (AV, AH). Either of these sets is fed to a gate (G) whose output is switched to a storage capacitor (C) and buffer amplifier (4). The switch is controlled from the output of a differential amplifier (3) with one input fed from a reference potential (P) and the other from the video output stage (2). The buffer amplifier output is connected to the black-level clamp circuit (D1, R1).