10 Jul
2007
10 Jul
'07
9:23 p.m.
From: Patrick Finnegan <pat at
computer-refuge.org>
On Tuesday 10 July 2007, der Mouse wrote:
There's no reason that you can't use a reverse-biased Si diode at its
breakdown (avalanche) voltage, as long as you kept the current to a
sane level (not a whole lot more than the current rating of the diode,
that is).
That's basically what a Zener diode is, anyways, just a silicon diode
with a precise breakdown voltage.
The main problem would be that a reverse-biased diode doesn't have the
same characteristics as a neon bulb... once you're back below the
avalanche voltage, it'll stop conducting in the reverse direction.
The higher voltage zeners have a slight negative resistance region.
The cross over point between the knee breakdown and the avalanche
is around 7 volts. We used to use 7.2 volt zeners as white noise
genrators because these had a mixture of knee and avalanche type
breakdown. If bias with a large limiting resistor and 9 volts, it would
produce niece white noise to align wide bandpass amplifiers.
One diode type could be used that is relatively easy to find and that
is a diac. These should make a nice oscillator. One just has to have
a high enough resistance to drop below the on current.
Dwight
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It's
an oscillator built around a capacitor and something with a
breakdown voltage, a neon lamp for example.
With a breakdown voltage, a (lower) extinction voltage, and such that
breakdown does not harm it (in contrast to, say, a reverse-biased
silicon diode, which would likely fry in such a circuit).