RGB-to-monochrome converter

72 This circuit offers impeccable monochrome images when driven by the digital RGB and sync signals of a high-resolution graphics card such as the one featured in Elektor Elec- tronics, issues from November 1985 to March 1986. Transistor T2 in the video combiner/ buffer ensures a short-circuit proof, 75Q impedance monochrome and composite video signal with an rms value of about 1V, as usual for con- nection to a monitor. The combi- nation of a PNP and an NPN transis- tor, Ti and T2 respectively, for ampli- fication and combination of video and sync typically exhibits a good response to the fast rise and fall times RG B-to-monochrome video combiner of these signals, and thus enables sufficient picture definition in the case of, for instance, text presen- tation at 80 characters per line, or high-resolution graphics appli- cations. The input circuit arrangement with Ti and the mixer resistors is a D/A converter in its most rudimentary form; the R, G, B, and I signals are ap- plied t...