The Versatile Midgets

The most exciting new development in electronics is the transistor, a tiny, simple device that can do the work of most vacuum tubes. Transistors are generally mounted in plastic or metal for easy handling, but the essential works of the smallest models are only one tenth of an inch long and fifteen-thousandths of an inch in diameter, hardly big enough to see without squinting. Last week Dr. A. E. Anderson of Bell Telephone Laboratories told a Manhattan meeting of the American Association of Aeronautical Engineers about the latest transistor progress. The airmen listened intently, because modern aircraft, especially military models, carry ever-increasing loads of vacuum tubes. Any chance of relief from this bulky burden is good news.

Transistors were invented 3 1/2 years ago by a research group under Bell's Dr. William Shockley, and are now being developed for practical use by another team led by J. A. Morton. Their theory is complex in detail and full of difficult quantum mechanics, but their general principle is fairly simple.

Between the Atoms. In an ordinary electron tube, electrons "boil" off a heated filament into a high vacuum. There, unhampered by clogging air, they dance around obediently in response to electrical forces provided to act upon them. A transistor has no filament or vacuum, only a speck of hard germanium cut from a silvery crystal. But the mobile electrons are there, flashing through the empty channels between the ordered atoms of the crystal fragment.

In the outer shell of its atom, germanium has four electrons. If the crystal were absolutely pure germanium, each of these electrons would be bound by a neighboring atom. But if an occasional atom of an impurity such as phosphorus, which has five outer electrons, is built into the crystal, one of its electrons is not bound, and so is free to move around. If the impurity is an element with only three outer electrons, there is a "hole" into which electrons from germanium can move under certain conditions. Every time an electron moves into one hole, a new hole is left. When the holes move through the crystal, they produce the effect of electrons moving in the opposite direction.

Points & Junctions. Some transistors (the "point contact" type) use only one kind of germanium with fine metal points pressing upon it. "Junction transistors" use both the germanium that has free electrons and germanium that has "holes." Both transistors act like electron tubes; they can turn alternating into direct current, amplify faint currents, generate musical tones, serve as relays; they even perform brilliantly as photoelectric cells, turning light into electricity.

All these chores are performed by the transistor with startling economy of materials and power. There is no glass envelope, as in an electron tube, and no complicated insides. The current price of germanium is more than $100 a lb., but so little is used that its cost is negligible.

The transistor's greatest advantage is its lack of a heated filament. Most of the currents that pulse through electronic apparatus are extremely small, but when they are amplified or relayed by a conventional vacuum tube, its filament consumes a full watt. It is the same, says Dr. Ralph Bown, vice president in charge of research at Bell Laboratories, as "sending a twelve-car freight train, locomotive and all, to carry a pound of butter." A transistor gets along with a millionth of a watt, not enough in most cases to make it faintly warm. The Bell men take a bit of blotting paper, chew it for a while, and wrap it moist around a 25-c- piece. When wires are clipped to this combination, it makes a battery strong enough to work a transistor.

In such complicated devices as radars and computers, which use hundreds or even thousands of vacuum tubes, supplying the power is a serious problem. The heat developed by the tubes is even worse. To keep the temperature down, they must be well spaced and cooled by an air stream. Transistors cause no such problems; they can be "potted" in plastic and whole arrays put close together.

Magic Trifle. Bell Laboratory has a two-stage transistor amplifier, complete with resistors and condensers, that is potted in a cylinder of plastic as big as a 3/4-inch section cut from a fountain pen. When a faint voice current is fed to this trifle, it gives a signal loud enough to blast the eardrum. Scores of such amplifiers could be packed in a coffee can. One device at Bell has transistors that do the work of 44 vacuum tubes. The whole thing is housed on a panel no bigger than the page of a novel.

The earliest transistors were skittish and unreliable. Now, says Bell, they are as reliable as conventional vacuum tubes, and much longer-lived. Some types are expected to work continuously for 90,000 hours (ten years). None are on the open market yet, but pilot plant production is under way. Bell is guarded about the cost but engineers are confident that they will prove cheaper than vacuum tubes.

Transistor enthusiasts speak of the future with electronic ecstasy. Replacing vacuum tubes, they say, is not the whole story: transistors will be far more versatile than vacuum tubes. There may be transistor amplifiers in telephone receivers. Airplanes and guided missiles can carry electronic equipment that is now too heavy and fragile. Transistors will give a new impetus to development of electronic-control apparatus for automatic factories. Perhaps the most exciting possibility is in the rapidly growing field of electronic computers. Transistors can be built, theoretically, almost as small as the neurons (nerve cells) that serve as relays in the human brain, and they react several thousand times faster. A "brain" built with transistors instead of vacuum tubes might out-calculate a regiment of Einsteins and still fit in the room where Einstein does his thinking.

This file is automatically generated by a robot program, so reader's discretion is required.