An eye for an i #317 Children

Lee de Forest invents the first triode

Lee de Forest holding a low power audion (left) for radio receivers and a high power audion (right) for radio transmitters.   | Photo Credit: Photo: Wikimedia Commons

Transistors are often dubbed as the nerve cells of the information age. As the active components of integrated circuits, any electronic device contains innumerable transistors as these semiconductor devices amplify, control and generate electrical signals. Making electronic devices, you might imagine, surely would have been very difficult without these minuscule devices then.

And yet, these transistors were invented only late in the first half of the 20th century. Before that, for nearly four decades, the key component for all radio, television, telephone and computer systems was an audion, a triode invented by Lee de Forest in 1906.

Takes to machines

Born in Iowa, U.S.A in 1873, de Forest was drawn towards machinery from a rather young age. His family moved to Alabama when his father took the presidency of the Talladega College for Negroes.

Since the white community avoided their family owing to his father’s efforts to educate blacks, de Forest only befriended black children in the town. He grew up happily, nevertheless, turning out to be a passionate gadget-maker by the time he turned 13. That was why even though his father had planned life as a clergyman for him, he instead took to the sciences.

After a not-so-great undergraduate education, during which he had to do odd jobs to supplement his scholarship and allowance from his parents, de Forest completed his Ph.D. in Physics in 1899. By this time, de Forest had become focussed on a subject which we now call radio and began conceiving an improvement upon the diode vacuum tubes that were used then.

Improves upon a diode

The existing diodes could rectify signals, but not amplify them and were also incapable of responding to small changes in electromagnetic radiation. In 1906, de Forest came up with the simple technique of adding a third electrode between the existing two, producing a three-element electronic valve similar to the two-element device already in use.

On October 20, 1906, de Forest presented the audion, which was the first triode, to a meeting of the American Institute of Electrical Engineers and received a patent for it by 1907. With its ability to both rectify and amplify to go along with its capability to be more sensitive to wireless signals, audions would go on to become an indispensable component of electronic circuits.

Cascades audions

In the years that followed, de Forest figured out how to cascade a series of audion tubes. By doing this (feeding the output of one to another through a transformer and so on), de Forest achieved amplification of radio signals way beyond what was done through increasing the voltage on a single tube. Both in the case of radio and telephonic long-distance communication, this amplification of an originally weak signal was a vital development.

Despite his successes with sciences and his colossal contribution to the broadcasting industry, de Forest turned out to be bad as a businessman and even worse at judging people. He tried and failed a number of times after setting up his own company, he was defrauded a couple of times by his own business partners and he spent heavily on his legal bills, having to fight lengthy patent wars. By the time de Forest died in 1961, he had had to sell off many of his patents to major firms, who then employed it profitably.

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No luck with the Phonofilm

In the 1920s, de Forest started working on a system for recording and producing sound motion pictures.

He developed Phonofilm and demonstrated it in theatres, without finding any takers.

Even though his Phonofilm was correct in principle, the quality of its operation was poor.

Within a few years, motion-picture industry soon converted to talking pictures. The sound-on-film process that was employed was similar to the one de Forest had used in his Phonofilm.

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Printable version | Jan 24, 2021 8:15:47 AM | https://www.thehindu.com/children/lee-de-forest-invents-the-first-triode/article25203083.ece

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