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From: John Popelish
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X-Mailer: Mozilla 4.7 [en] (Win98; U)
Subject: Re: Easy question, I hope!
Date: Thu, 07 Nov 2002 10:52:22 GMT
NNTP-Posting-Date: Thu, 07 Nov 2002 05:52:22 EST
> Hi people,
> I have been looking around for the last few days for a particular
> application of electronics that seems so fundamental in nature, yet I
> can find no schematic or design that cites it anywhere I look.
> What I'm looking for is essentially a low-voltage version of a
> spark gap. If enough voltage is applied across it, current will flow,
> else, no current flows. Here are its properties:
> 1) Uses no external power source
> 2) dissipates little or no energy in "off" mode
> 3) resistance approaches infinity when the applied voltage is less
> than V0
> 4) resistance goes to zero when applied voltage is greater than V0
> I was pondering that a Zener diode might get the job done, but I'd
> like to hear your opinions, too.
You have a few choices of solid state device that might be what you
are thinking about. Some continue to conduct as the voltage drops to
lower than the firing voltage (have negative resistance and can be
used to generate pulses) until the current drops below some minimum
holding current and some only conduct as long as the voltage is above
some threshold (have positive resistance and will not generate
Take a look at the SIDACtor, SIDAC and DIAC from Teccor:
these are all negative resistance devices.
Zener diodes are good examples of positive resistance nonlinear
devices that conduct very little current till a threshold voltage is
reached. They are also available in symmetrical versions that have
the same characteristic in both directions. Take a look at the
transient voltage protector diodes from Diodes Incorporated. For
All these and lots of zener diodes are available from Digikey.
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