I'm amazed at how much traffic this has generated.
Thanks Brooke, you're exactly on-topic as usual.
As I said originally, I wanted a quick-and-dirty-and-cheap, and I'm
using an SMMD-835 SRD. Making up the test layout tonight.
I'm starting with a 100 uA bias on the diode, and a 20 pF diode-to-load
coupling cap, driving the SRD with a 5V 1Mhz square-wave.
I'm also going to try the 2N3904 Vce-reverse-bias avalanche idea just
for fun.
I'll post again after I have some results.
PS - as I've mentioned before, I trim these things. I hate the
endlessly-requoted replies, impossible to parse what's actually been said.
--- Brooke post, trimmed --
Hi:
The idea with a step recovery diode is that during forward bias the
diode stores charge. When the polarity reverses the diode continues to
conduct until the charge has been depleted. At that time the diode
stops conducting and opens.
Suppose this was done using a square wave. The length of the positive
(charging) half of waveform needs to be long enough so that the diode if
fully charged (a function of the diode lifetime and charging current).
Then on the negative half (discharging) when all the charge has been
extracted the diode turns of making a sharp edge. So the diode lifetime
is important in relation to input drive frequency. For a sinewave drive
the lifetime should be about 1/4 the period at the recommended drive level.
--
Bill Ezell
----------
The day Microsoft makes something that doesn't suck
will be the day they make vacuum cleaners.
Or maybe Windows 10.
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