| 摘要 |
PURPOSE:To make the vertical amplitude of a video signal invariably constant on the screen of a cathode-ray tube by using an operational amplifier for an amplification control circuit and controlling the source voltage of a saw-tooth wave voltage waveform generating circuit with its output, and switching the input circuit of the operational amplifier according to the contents of an input signal. CONSTITUTION:The operational amplifier is used for the amplification control circuit 8 which controls the source voltage of the saw-tooth wave voltage waveform generating circuit 1, its input/output circuit is provided with a switch circuit, and circuit connections are switched with the output (j) of a control signal generating circuit 9. Namely, the source voltage of the saw-tooth wave voltage generating circuit 1 is made constant by controlling the source voltage level of the charging and discharging circuit of the saw-tooth wave voltage generating circuit 1 so that the crest value of a deflecting current flowing between the terminals of a negative feedback signal detection resistance 5 is held invariably constant or outputting a value determined unequivocally for the value of the value of a bias voltage (l) to the output (h) of the amplification control circuit 81 by cutting off the output signal (g) of a rectifying circuit 7. Consequently, the size of the vertical image plane of an image appearing on the CRT screen is held constant at all times. |
