| 摘要 |
PROBLEM TO BE SOLVED: To prevent the brightness of display on a CRT screen from being reduced even when the amplitude of video swing of a cathod drive for a cathod- ray tube(CRT) is reduced in order to extend a frequency characteristic in a video amplification circuit for a monitor capable of displaying RGB signals and video signals for multimedia. SOLUTION: In the case of driving the video amplification circuit by a mode suited for amplifying an input video signal in a relatively wide band, a relatively small resistor (a parallel connection circuit of resistors R3, R1) is selected by a gain switching circuit 4 to be used also as a resistor switching circuit, relatively low power supply voltage 15 selected by a power supply voltage switching circuit 5 and the set contents of a bias voltage switching circuit 6 and a screen voltage control circuit (consisting of a transistor Q5 and resistors R8, R9) are controlled in a direction for relatively improving the luminance of the CRT. |
