Why vacuum tubes can not be made small

[planety_vuki]

Why vacuum tubes can not be made small sized ? I'm talking about millimeter to micrometer or maybe even nanometer size ranges ? Or can they be ?

This way electronic devices, for example computers, could be made they way they were made in the past but much smaller.

 

[phinds]

Even if you COULD make VTs really small, the glass enclosure for one would be HUGE compared to a single transistor on a wafer, AND the power consumption would be enormously higher. What could possibly be the point of reverting from an excellent technology to a vastly inferior one?

 

[planety_vuki]

Even if you COULD make VTs really small, the glass enclosure for one would be HUGE compared to a single transistor on a wafer, AND the power consumption would be enormously higher. What could possibly be the point of reverting from an excellent technology to a vastly inferior one?

I think they would work without glass envelope for every each of them, istead the whole chip would be inside evacuated glass. Second, there is really no strong reason, I just like vacuum tubes, their operating principle is simpler than transistors. Also I simply just wander if they can be made at small sizes. I mean, would it work ?

 

[trollcast]

there's research currently ongoing into making nano scale vacuum channel transistors (effectively a sort of nanoscale vacuum tube)

http://www.newelectronics.co.uk/ele...ogy-is-being-deployed-at-the-nanoscale/45695/ - An article from a electronics magazine that describes them and how they work

http://apl.aip.org/resource/1/applab/v100/i21/p213505_s1?bypassSSO=1 - A more technical view of them

 

[sophiecentaur]

FETs are not a million miles from a vacuum tube, aamof. They work on the effect of the volts on the gate, like the grid of a valve.
At the other end of the power range, there is still no substitute for the several hundred kW Radio Transmitting Valve or the 50kW UHF Klystron, both, very much vacuum tubes. There's no better way of powering your microwave oven than the Magnetron, still.
Thermionic is far from dead, chaps. It's horses for courses.

 

[Averagesupernova]

Sophie hit the nail right on the head. As soon as I saw the title for this thread I thought of FETs.