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It has only two connections, you can regard this a
"Vacuum State" Zener Diode.
Physically it works by comparable effects! It
works by Avalanche effects also, and has the same connections.
(Cathode + Anode) . It is used in circuits exactly the same way.
Actually is has been
forgotten, that the semiconductor version Avalance effect is a dirty one, whereas the vacuum version works near-perfect.
The method in silicon is, that
the isolation barrier will get wider when the negative voltage gets
larger. Then on purpose the isolution barrier gets so wide, it will start to touch the electrodes, and that's when conductance starts. So the Zener effect in silicon material l is nothing else than controlled
break down of the Diode, which is normally an undesired effect. However, with a gas tube it is no undesired effect. It is why they are made.
There are several kind of gas tubes. The most important are:
- Voltage regulators. These are for parallel stabilisation. They give the required voltage within a specified range. For instance OC3 gives 105 Volts, from 5....40mA. I tried to use them above, and what you see then, they cannot keep the voltge very well. (same bad curves as silicon Zener Diodes start to develop above 20mA). So stay within the specified ranges, and they're awfully precise.
- Voltage referances: These are not intended as regulators, but these have an specific current, that you must give to them, and they will give a reference voltage.
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Silicon Diode
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Gas tube
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Precision
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Forget it. When you take a 120Volt Zener diode, you will end up
with 115..... 125 Volt. Depending on age, ambient temperature and
actual current, the brand the tolerance of the diode itself.
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I use a new, 950 Euro Agilent precision digital
voltmeter to measure the output voltage, and it is only the
5th (!!!) digit that is changing. All tubes, all brands.
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Stability over time, like 30.000 hours
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Values will change over time, when used hot. Over time all crystals will change (no matter what crystal). Heat
will make the change go faster. With siliicon crystals, the Zener value changes.
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Excellent
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Temperature drift
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Try it, and you will not like what you see.
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Excellent
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Reliability
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Any overload, it is dead.
If you have done repair work, you will have know that Power Zener diodes
are quite unreliable things.
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double power dissipation tolerated, they recover normally when you reduce power again.
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Noise
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Very High by default.
The Zener diode turning into a noise source is a typical
defect.
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Low noise
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Price
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5..20 cents
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2...20 Euro
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Speed
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What speed?
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Ultra
Fast
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as you can see from the above table, silicon regulators is something to kick out if you can and replace it by a gas tube.
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