Amplificateur déformant pour une installation de télévision.

摘要

687,376. Non-linear valve circuits. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. June 15, 1951 [Sept. 29, 1950], No. 23940/50. Class 40 (vi). A television signal with positive-going synchronizing pulses is fed to the grid of a valve V1 with negative feed-back, amplified signals being supplied over a rectifier D2 to the grid of valve V2 to reduce the negative feed-back and cause positive feed-back during the synchronizing pulses, a further rectifier D3 applying bias to valve V2 to distort the signal when a predetermined level of video signal is reached. The circuit is particularly adapted for increasing the amplitude of the synchronizing pulses and the gain of components near the black and white levels. Resistor R2 in the cathode lead of valve V1 provides negative feed-back, the valve V2 acting as a resistance since the grid is tied to the cathode over the low resistor R3. The signal from the anode of V1 is fed to the grid of valve V3, the synchronizing pulses causing diode D2 to conduct, carrying the grid of valve V2 negative. In this manner, the cathode of valve V1 is driven negative so that the synchronizing pulses are increased, the valve V2 being driven beyond cut-off. During the video part of the signal, the input is negative-going causing the cathode of valve V2 to fall. Near the maximum negative amplitude biased diode D3 conducts to hold the grid potential of valve V2 constant, thus reducing the negative feedback operating on valve V1 due to the common cathode resistor R2. Similarly the diode D1 may be caused to conduct for lower amplitudes of the video signal.