| 摘要 |
PURPOSE:To lower the amplification degree when an cathode current excessively flows and to prevent the generation of a blooming by having a means for detecting the cathode current and automatically controlling the gain of a video amplifier circuit by a voltage detected according to the scale of the cathode current. CONSTITUTION:Collectors of emitter follower transistors 26-28 are grounded through resistances 32-37, the resistance 32 detects a voltage for adjusting a white balance and at the same time, a divided voltage is generated at a connecting point with the resistance by the resistance division. When the voltage of the resistance 35 is increased by one diode, the diode 38 is conductive, a base voltage of a transistor 16 is raised, a current of R is lowered, the voltage of a collector resistance is raised, and a cathode voltage is raised, so that the cathode current is lowered. The similar operation is performed on other G, B signals. Thereby, during the white color signal, the cathode voltage is raised, the cathode current is lowered, the blooming is not produced and the picture quality of a satisfactory gradation can be obtained.
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