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News Picks : NASA's high-speed transistor uses same principle as vacuum tubes

By: Physics Today
25 June 2014

Ars Technica: Vacuum tubes were a key piece of many electronics prior to the development of transistors. They consisted of two electrodes—the cathode and the anode—separated by a grid that controlled the rate of current flow based on the voltage supplied. To cause the cathode to release electrons it had to be heated, which drew a lot of power. The entire setup was arranged in a vacuum in an airtight glass bulb to prevent the electrons from ionizing atoms between the electrodes. Now, researchers at NASA have created a nanoscale transistor that structurally resembles a vacuum tube. However, because of its small size—the electrodes are separated by nanometers instead of millimeters—there is no need for a vacuum because there is little chance that any electrons will be able to collide with air molecules. It also doesn't require a heating element; electrons can be released by placing the cathode in a static electric field. The resulting prototype vacuum-channel transistor has a switching speed of 460 GHz. That puts it in the frequency range between 100 GHz and 10 THz, known as the terahertz gap, in which traditional transistors have difficulty sending and detecting signals. Transistors operating in this range could allow for the creation of devices used for imaging and signal detection in a part of the spectrum that had been hard to access.


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