This question is in regards to signal attenuation on high speed data lines like RS-485 (and any others as well). I'm new to the signal world, so please bear with me here.

Are there some useful concepts and general formulas, to help me get an idea of the degree of signal attenuation which may result from adding series resistances and parallel capacitances (like from a TVS) to a data line. When I model the situation as an RC low pass filter, the usable frequencies I get are way too high (in the Terahertz range). I know from my reading that typical cutoffs are in the 1-100 MHz range so THz is definitely insane.

It would be nice to not only have some useful intro theory, but also some realistic values that engineers typically use and design with.

Thank you.

  • \$\begingroup\$ At the UHF end there are SMD type TVS diodes with 1.5pF of capacitance, which allows frequencies up to 2GHZ. But they can handle only minor transients. At lower frequencies the capacitance and physical size can safely go up, so it will tolerate stronger transients. \$\endgroup\$ – Sparky256 Feb 16 at 23:57
  • \$\begingroup\$ 10 ohms and 10pf are 100 picosecond, or 1.6GHz F3dB. What do your sims show? \$\endgroup\$ – analogsystemsrf Feb 17 at 1:36

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