COMPLETE RGB VIDEO SYSTEM

A typical connection diagram for a red, green, blue video amplifier system is shown in Figure 2. To achieve optimum contrast

tracking, a master slave contrast connection is utilized. This is accomplished by connecting pins 1 and 2 of all three preamplifiers

together and using the contrast control of one channel to vary the contrast of all three channels simultaneously. White balance is

achieved through individual drive controls. Black level can also be adjusted for each channel by adjusting the voltage at pin 17. If

the cathode is AC coupled, the video signal is DC restored at the cathode. In that case black level clamping can be accomplished

by biasing pin 17 to the desired black level. The video output pins of the MSK 620 rests at approximately +3.9VDC and the input

of the MSK 640 must be biased at approximately +1.55VDC. D1, D2, D3 and Q1 act as a level shifting stage to match the DC

level requirements of the preamplifier and the driver. Black level control is accomplished with R8 and R9 sampling the output and

feeding it back to the clamping section of the MSK 620. This scheme provides black level control superior to locally sampling the

MSK 620 output and feeding that back to the clamping section.

Rev. A 8/00

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