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High Speed Amplifiers for Video Applications Pt 3 Slide 11

At the receiving end R1 terminates the cable in its characteristics impedance of 100 ohms and one section of an LMH6643, again, converts the differential input into a single-ended output at R7. Up to this point, you have the original signal back from the source back through the length of cable and with an inversion of gain. In other words, a gain of -1. The second LMH6643 to the right is then used to reverse the signal again for proper polarity at the RCA output. Because of the high frequency attenuation that an appreciable length of cable exerts on a video signal, a series RC network is placed across R7 which is seating the input of the second stage in order to provide high-frequency peaking. The amount of peaking can be adjusted by tuning the values of these components. When viewed on a display, a high frequency test pattern would be a good guide as to how much peaking would be optimal.

PTM Published on: 2011-11-21