Hi again Guys,

I have been reading a bit about valves on web pages such as Wikipedia, etc.

Why are valves not referred to as Solid State,
when semiconductors require the movement of
electrons for their operation too?

Thanks, Brek.

Apart from a few cold cathode types, valves do not operate without being heated. This alone puts them outside the classification of 'solid state'.

Thanks Brad,
A correct definition of the term Solid State would help as a starting point.
had to go look that up. I always thought that it just meant no moving parts (relays, gears, etc).

We are one of the few countries that use the word "Valve"
which can be confused with other things in engines & plumbing.

Most every where else there is the term "electron tube" often "tube" (USA) or, thermionic tube /valve.

This as it requires a heater (thermal) to cause electrons to be expelled. from the cathode (plasma flow... blue).

The nomenclature for valves precedes transistor in which there are not the same physics.

Personally I dislike the term tube as the devices are not tubular but are technically a valve because they are used to regulate a flow of electricity through them. Sir John Fleming referred to them as thermionic valves and this is no doubt why Australia and New Zealand followed suit. To my knowledge only the US and Canada call them tubes.

Early valve development took place on both sides of the Atlantic. The English called them Thermionic Valves & the Americans called their version Vacuum Tubes.

The German word for valve is Röhre, which means tube.
In Dutch they are Elektronenbuis which translates to Electron Tube (buis = tube).

The old timers here just call them bottles!

Both valve & tube are valid words to describe a electron emitting device.

The term Solid State is a physics term rather than electronic. The study of solids is a discipline within Physics.

The theory of transistors (and the practise) is based on the movement of electrons and holes through solids eg. germanium and silicon ... rather than electrons through a vacuum. Very different principles involved (chemical doping, atomic structure, depletion zones etc versus wave/particle/electromagnetic theories).

Cheers,
Ian

.. so we arrive at the distinction between solid (transistor) and vacuum (valve, tube, bottle) as the medium through which electrons pass under controlled conditions.

Were there ever "thermionic valves" that did not employ a vacuum - eg any that used an inert gas like nitrogen?

Glass is fragile and pressure vessels including radio valves are under constant stress from the difference in pressure inside and outside the glass. In the last week I've replaced a)a thermos vacuum flask that shattered and b)a fluorescent lighting tube that hadn't shattered (yet). The replacement for that brittle fluoro tube is a LED replacement tube that fits the standard fluoro mount, but includes a small transformer and rectifier at each end of the tube to power rows of LEDs. The starting capacitor is replaced with a unit that just shorts the contacts. More directed light, half the wattage, and the tube is polycarbonate that bends rather than breaking - safer and cheaper to run. However, the PSUs do emit a 100Hz hum so the LED tubes would not be ideal where silence matters.

Maven