K
Ken Smith
One trick I've used to mitigate Zener capacitance is to use a regular
small-signal diode in series with the Zener (with the appropriate
polarity). Typically the forward capacitance of the small-signal
diode is much lower, so you get two capacitors in series. Very handy
for a rude-and-crude clamp at an opamp's output, but I've never
tried it in a transient-suppression application.
You have to provide biasing.
Fortunately, the diodes fail shorted, usually.