|
|
|
| Current Issue |
|
|
| Resources |
|
|
|
Vacuum Tubes: The Sequel
| Article
# : |
17075 |
|
|
Section : |
NATURAL SCIENCE
|
| Issue
Date : |
8 / 1990 |
2,079 Words |
| Author
: |
Hank Hogan
Hank Hogan is a science writer in Austin, Texas. |
Researchers around the world are busy resurrecting an electronics dinosaur. Borrowing the tools and techniques of modern solid-state electronics, they are reviving the vacuum tube. Unlike the large, warm glass tubes of memory, these new vacuum tubes are too small to be seen by the unaided eye. With capabilities beyond that of its ancient brethren, this new incarnation of an old technology promises capabilities that cannot be met by transistors, the solid-state cousins that originally replaced vacuum tubes. This technology is different enough to warrant its own name, vacuum microelectronics, and it may ultimately impact each one of us.
A Melding Of Approaches
According to Henry F. Gray of the Naval Research Laboratory, who coined the term vacuum microelectronics in 1988, the field attempts "to merge the advantages of the solid-state industry, which are fabrication and processing with the advantages of vacuum ballistic transport, which is the advantage vacuum electronics."
The traditional vacuum tube was the mainstay of electronics from the beginning of the century until the advent of the solid-state transistor in the 1950s. Inside the vacuum, which was maintained by a glass tube, the device had three electrodes: a cathode, an anode, and a gate. Heating the negatively charged cathode boiled electrons off it and those electrons then darted to the positively charged anode. Along the way they passed the gate. A small current applied to the gate deflected the much larger cathode-to-anode stream of electrons. Since the resulting current at the anode was an amplified version of the gate current, the vacuum tube was an amplifier. Applying a larger current to the gate shut the stream off. That made the vacuum tube an on-off switch.
With amplifiers and switches, engineers had everything they needed to build complex electronic devices. And build them they tried. The problem was that vacuum tubes were hot, unreliable, bulky power hogs. Digital computers that depended on this technology required a constant stream of replacement tubes and, despite the best efforts of their sweating human caretakers, suffered what would today be considered an incredible amount of down time.
Something smaller, more reliable, and less power hungry had to be found. The eventual answer was the solid-state transistor, followed by the integrated circuit. But in the late 1940s and 1950s, Ken Shoulders of MIT and later SRI proposed a different approach. He wanted to
...
Read Full Article
Look for this article in Ask.com
|
|
