LUMINANCE ADJUSTING CIRCUIT

• Main Authors: KIMURA YUUICHIROU, OOSAWA MICHITAKA
• Format: Patent
• Language: English
• Published: 13.05.1985
• Subjects: ELECTRIC COMMUNICATION TECHNIQUE; ELECTRICITY; PICTORIAL COMMUNICATION, e.g. TELEVISION

PURPOSE:To obtain a luminance adjusting circuit with ease of adjustment while keeping excellent white balance by providing a variable gain amplifier inputting a luminance adjusting voltage in common to three colors R, G, B and amplifying each color at independent gain and giving output so as to absorb variation of a gradient of an optical output characteristic. CONSTITUTION:The operating state of transistors (TRs) 10, 11 are divided into three modes depending on its base potential VD; (1) (VB-2VBE)<VD<VB, (2) VD<(VB-2VBE), (3) VD>VB, where VBE is a base-emitter voltage. The mode is set to the mode (1) by adjusting resistors 13, 14 at first. Since the TRs 10, 11 are both cut off, the cut-off voltage is adjusted by adjusting a resistor 7 of each color so as to match the white balance. Then the mode (2) is set by adjusting the resistors 13, 14 similarly, and in this mode, the base potential VD is minimized (maximum luminance), the gain of the differential amplifier comprising the TRs 9, 10 is adjusted by using a resistor 8 so as to attain white balance.