On 2025Dec 25,, at 12:32 PM, Martin Bishop <[email protected]> wrote: > > Series R on logic outputs are a classic "taming" mechanism, they also provide > access to the net for more extreme measures (eg C to ground). Usu 22R or 33R > close to the driver to bring the probable source impedance to 50Z - matching > the nominal track impedance. The design may be evolved to include parallel > (DC) termination or AC termination (series R & C) for multidrop loads. For > 2025 circuits much of this is moot, the track lengths are so short, in the > 1980's it was different ... > > IBIS models for devices of interest and the wisdom of HoJo's oeuvre are the > classic references > https://www.amazon.co.uk/High-Speed-Signal-Propagation-Advanced/dp/013084408X/ref=sr_1_1
The series R/L in a signal line for parisitic oscillation/ringing suppression actually goes back to the early tube days, well before logic, where they can be found on tube grids, esp. power amps, even audio freq.
