I'm trying to analyze a circuit from the ~40 year old TI TMS9928/29 Interface to Color Monitors application note. It shows how to convert the (almost) Component video straight from the graphics chip to RGB or Composite out.
All three of the YUV video lines have what is presumably a filter (with identical component values) that I wasn't able to find in any of the filter recipe lists in AoE or elsewhere:
(I'm guessing C14 is an unrelated coupling capacitor.)
It looks vaguely like a low-pass filter, but tinkering around in LTSpice, I wasn't able to make the output look any different than the input (above, at, or below the ~3MHz signal frequency).
Walking through the application note schematic is pushing the limits of my analysis ability (in a productive, trial-by-fire sort of way), but this one has me stumped. Thanks!
EDIT: Of course it's not filtering the voltage; that whole top rail is the same node! (This is how you can tell I need more practice.) Wikipedia says "the parallel RC circuit is generally of less interest...", so maybe a better question is "Why did the TI engineers put those components there?"