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High Spped Amplifiers for Video Applications Slide 2

Here is the standard composite video waveform which is standard for both TV and standalone monitors. Timings and levels specified correspond to the NTSC standard which is not far from the values used in the PAL system. Note that to preserve color integrity the analog processing path should faithfully reproduce the 3.58 megahertz color modulation at any intensity or voltage level. The true reproduction of this modulation involves both amplitude and phase since these control the color depth and hue, respectively. This is what is referred to as Differential Gain and Differential Phase, the DG and DP in the literature. Most professional video processing amplifiers require DG and DP to be less than .1% and .1 degrees, respectively. In PC multimedia applications where the display information is in the form of analog red, green, blue or RGB voltage levels, the color sub-carrier is not used. In such a system, the sync and video levels for each color are the same as what is shown here minus the 3.58 megahertz carrier. We find that many designers of such systems still rely on the DG/DP specifications in their evaluations and their part selections even though, strictly speaking, the displayed image does not use this encoding scheme.

PTM Published on: 2011-11-02