The return of the vacuum tube?


May 28, 2012

Researchers are working on a vacuum channel transistor that can combines the best traits of transistors and vacuum tubes like those pictured (Photo: Shutterstock)

Researchers are working on a vacuum channel transistor that can combines the best traits of transistors and vacuum tubes like those pictured (Photo: Shutterstock)

Most people associate vacuum tubes with a time when a single computer took up several rooms and "debugging" meant removing the insects stuck in the valves, but this technology may be in for a resurgence with news that researchers at NASA and the National Nanofab Center in South Korea are working on a miniaturized "vacuum channel transistor" - a best-of-both-worlds device that could find application in space and high-radiation environments.

Vacuum tubes, or thermionic valves, have almost disappeared from our day-to-day life, save for some purist sound rigs and high-power radio base stations. Their replacement - solid-state transistors - are easier to manufacture, cheaper, lighter, last longer, and consume much less power. Valves, on the other hand, are more robust in high-temperature and high-radiation environments and yield a higher frequency/power output than standard transistors.

NASA/Nanofab researchers are developing a device the combines the best aspects from both vacuum tubes and solid-state transistors. Their prototype "vacuum channel transistor" is only 150 nanometers in size, can be manufactured cheaply using standard silicon semiconductor processing, can operate at high speeds even in hostile environments, and could consume just as much power as a standard transistor.

In a vacuum tube, electrons flow from the cathode to the anode by thermionic emission, the heat-induced flow of electrons. This means the cathode needs to be heated before it can emit electrons. The heating process requires a lot of power for the conventional macroscale tubes, but the energy expenditure drops dramatically as the device becomes smaller and the gap between the electrodes shrinks.

The nanoscale vacuum channel transistors being developed can operate at less than 10 volts, a significant improvement over standard tubes. The researchers say that, once the gap between the emitter and the collector is further reduced to only 10 nanometers, the power requirements will drop to less than a volt, which would be competitive with modern semiconductor technology.

The device also offers significant gains in terms of how fast the electrons can pass through. In semiconductors electron speed is limited to about 500 km (310 miles) per second, but in the vacuum they could travel at almost the speed of light - 600 times as fast.

This new technology could be used for sensing hazardous chemicals, noninvasive medical diagnostics, high-speed telecommunications, as well as in extreme environment military and space applications.

The results were published on the journal Applied Physics Letters.

Source: Eureka Alert / AIP

About the Author
Dario Borghino Dario studied software engineering at the Polytechnic University of Turin. When he isn't writing for Gizmag he is usually traveling the world on a whim, working on an AI-guided automated trading system, or chasing his dream to become the next European thumbwrestling champion. All articles by Dario Borghino

Just think if you made those micro vacuum tubes out of molybdenite instead of silicon you should be able to make them 75nm. But then you might also make the vacuum transistor out carbon nanotubes with a nanowire base where the ends count as the anode and cathode or by splitting it into two nanotube sections, and a micro base in between the two tubes. The other idea is to use a thorium base vacuum transistor where by the decay of metal makes the tube conduct electrons.

Travis Moore

Welcome back in a new body dear Vacuum tubes!

Kirill Belousov

"Vacuum tubes...have almost disappeared from our day-to-day life, save for some purist sound rigs and high-power radio base stations"

What?! Every (decent) guitar amplifier on the planet using vacuum tubes, that makes for a LOT. These aren't amps used by purists, they are everything from 1 watt amps used by kids to 100 watt amps. Even some Overdrive and Distortion pedals these days include 12AX7 tubes. Check every stage of every gig and every bedroom guitar player's rig.

Jonathan Bloomer

But will the nanoscale vacuum channel transistors be more or less susceptible to an EMP event?


I remember this idea. it must be 10 years since I read about it.

Stewart Mitchell

Extending upon Jonathan's remark: most households use a very large, very powerful vacuum tube: every microwave oven uses a magnetron tube.

Joris van den Heuvel

EMP events will likely be harmless to tubes.That is why early Russian jet fighters had an advantage over western designs: they used vacuum tubes while the west had "advanced" to transistorized circuits,which are definitely vulnerable to EMP.


Vacuum nanoelectronics

'can be manufactured cheaply using standard silicon semiconductor processing'..... because they do not have the complicated structure/composition of semiconductors ?

Yes, it is inherently EMP-proof, which alone is reason enough to incorporate it in critical no-fail functions; Anyone not worried about EMP weapons should Google 'Carrington Event' and read about naturally_generated EMP.

Obsolete equipment may get a new lease on life producing this circuitry at prices even 3rd world countries can afford, and while it cannot match the speed/complexity of semiconductor circuitry, it can be used to build general-purpose microcomputers adequate to their needs.

M. Report

I worked at Fender Musical Instruments in Fullerton, Ca. back in the late '60's. I also played guitar for a living for twenty years, almost all of it with my trusty Fender Super Reverb and/or my Fender Bandmaster. (The former with a single Gauss 15" Guitar [not Bass] speaker, and the later with an Alembic B-12 w/two Gauss 12" Guitar speakers.) Anyway, it'll be nice to find an alternative source for 5881/6L6GC's, 7025's, 12AX7's, 6679/12AT7's & etc., besides Sovtek. (My rectifier tube socket was rewired w/solid state components by Nic Grabien at Stars Guitars when we both worked there in the late '70's.) Anyway, I was on stage a few weeks ago and every one, player and sound tech alike, were just in love with the sound of my genuine tube powered amps. Sometimes, you just can't improve on perfection. No matter how "Technical" you get.

Myron J. Poltroonian

re; michael_dowling

The Russians built transistors as soon as they had reliable ones.


There's a good article in recent Electronic Design magazine, on why tubes sound different. Answer: low damping and transformer filtering; you're hearing the ringing and resonances of the speaker, not the "warmth" of the tubes. Transistors are low impedance voltage sources.

Captain Obvious
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