| 摘要 |
PURPOSE:To enable controlling of a beam current with less power consumption by providing a power source for giving voltage between the cathode and first grid of an image pickup tube independently of a power source for setting cathode potential. CONSTITUTION:A power source 23 supplies DC voltage of, for instance, 17V and is connected between a collector floated from the earth and a cathode 3 by separating the collector of a transistor 15 from the earth so as to set the cathode 3 side to negative polarity. A power source 24 generates DC voltage of, for instance, 10V and is connected between a negative terminal of conventional power sources and the cathode so as to set the cathode 3 side to positive polarity. When voltage drop due to a resistor 17 is neglected, the voltage of the first grid 4 against the cathode 3 changes arbirarily from the positive voltage determined by the power source 23 in accordance with the state of conduction of a transistor 14 to the negative voltage determined by the power source 24. |
