Browse Prior Art Database

Multiple Gray Level Video Amplifier for Display Monitor

IP.com Disclosure Number: IPCOM000100106D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 4 page(s) / 95K

Publishing Venue

IBM

Related People

Nakano, M: AUTHOR [+2]

Abstract

Disclosed is a multiple gray level video amplifier for CRT(cathode ray tube) display to implement both a fast response and a user friendly brightness and contrast control function.

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Multiple Gray Level Video Amplifier for Display Monitor

       Disclosed is a multiple gray level video amplifier for
CRT(cathode ray tube) display to implement both a fast response and a
user friendly brightness and contrast control function.

      Fig. 1 shows a function of the brightness and contrast control
according to a multiple gray level video amplifier disclosed herein.
The total brightness can be changed without altering the contrast
ratio by adjusting the brightness control, and the contrast ratio can
be changed without altering the highest intensity level and a black
level by adjusting the contrast control.

      The amplifier has a conventional digital-to-analog converter
(DAC) structure combined with the contrast and brightness control
circuit with the above function and an analog video amplifier.

      Fig. 2 shows an example of a circuit for a 2-bit digital video
amplifier which provides 4 gray levels: 1st (black), 2nd, 3rd, 4th
(highest intensity) levels.  Three current switches (Q3 and Q4, Q5
and Q6, and Q7 and Q8) distribute a current which flows into a
variable current source.  A current, I(Q3)+I(Q5)+I(Q7), flows through
transis tor Q1 as IC1, and generates an output voltage by a load
register R1.  A 2:1 current mirror (Q9, Q10, Q11) and Q12 are
provided between the current switches and the current source to
provide 2nd and 3rd gray levels and to change these gray level's
intensity by the contrast control.  Each transistor of the...