| 摘要 |
PURPOSE:To make the best use of the advantages of a gamma compensating circuit utilizing the nonlinearity of a diode and to ensure a stable and accurate operation at all times, by detecting the black level of a video signal obtained after gamma compensation and performing feedback control to the working point of the diode in the direction where the black level of the video signal is converged to a prescribed value. CONSTITUTION:Amplitude is detected for a clamp pulse (b) which is contained in a video signal (e) emerging at the output out after gamma compensation, and the result of detection is fed back to the working point of a diode 6 for gamma compensation. Then the amplitude of the pulse (b) contained in the signal (e) is converged to a prescribed value decided by the clamping voltage E81 and the comparing voltage E82. As a result, the diode 6 always works at a fixed level of terminal voltage. This process ensures the operation with optimum compensating characteristics at all times and with no change of gamma compensating characteristics which is due to a temperature change, etc. |
