| 摘要 |
PURPOSE:To suppress the disorder of a screen during channel switching as much as possible by providing a clipping circuit for clipping a video signal and clipping a video input signal at a voltage level a little bit lower than the sink top level of a synchronizing signal. CONSTITUTION:A clamp pulse generating circuit 15 outputs clamp pulses C to clamp a pedestal level to a constant value. When channels are changed, it takes a considerable time to clamp the signal with the output of the clamp pulse generating circuit 15 because of a transient response waveform E generated by a VIF circuit 4. coupling capacitor 7, etc., and the screen becomes stable. For the purpose, the clipping circuit 18 is connected to the input of a video signal processing circuit 14 and a clipping level is determined with divided voltages of resistances 9 and 10 to clip the video input signal through a diode 11. The clipping level is set a little bit lower than the synchronizing signal (sink top) of the video input signal. Consequently, there is normally no influence upon the video input signal and this device operates effectively on a transient response during channel switching.
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