[snip] [snip]
Aha! A rare occasion. You actually ask a cogent question rather than baiting.
Flyback diodes DO increase the time it takes for the field to collapse. I don't know what effect it has on _opening_time_of_contacts_ (slew rate), but it certainly inserts a _delay_ in opening.
In CMOS relay driver chips that I designed for Ethernet use many years ago I did the following (for two reasons):
(1) Diodes, for flyback use, don't exist on a CMOS process that don't also have nasty parasitic (and destructive) current paths.
(2) Speed was of the essence for releasing the relay.
So I devised a scheme where the voltage was allowed to rise as much as safely possible on the output device, then turn it back on to prevent further rise (in essence an active clamp).
Since this allows significant reverse voltage on the coil, the field collapses much more quickly than with a flyback diode.
...Jim Thompson