Lee De Forest was born on August 26, 1873 in Iowa. His father was a minister and dreamed that his son would one day follow in his footsteps. The family moved to Alabama after his father was appointed president of Talladega College, a primarily black school.
After graduating from Mount Hermon School, De Forest applied at Yale University and was accepted in 1893. He studied electrical engineering and started to work on inventing things. While experimenting one day, he accidentally shorted the school's electrical system and blacked out the entire campus. As a result he was suspended for some time, but eventually he was able to graduate with a Bachelor's degree in 1896.
After graduation, he continued studying at Yale, receiving a Ph.D. in electrical engineering in 1899. His dissertation focused on radio waves, one of the hot topics in science at the time. In 1906, he invented the "Audion Tube", a dual electrode vacuum tube that was specifically designed to amplify radio signals.
De Forest was a charter member of the Institute of Radio Engineers, a group of engineers and scientists that were interested in radio transmission and reception. The group later evolved into IEEE, the modern organization of electrical and electronic engineers.
In 1907, he developed a version of his Audion tube with three electrodes instead of two. The tube became known as the De Forest valve, more popularly known as the triode. The triode was essentially a diode with a metal grid between the filament and plate. The new configuration made it possible to use the triode for amplification and switching (much like modern transistors).
In 1916, De Forest filed a patent for a regenerative circuit, but had to fight another inventor, Edwin Armstrong, who had already received a patent for the idea in 1914. The lawsuit extended for twelve years, eventually reaching the United States Supreme Court. The final ruling was in favor of De Forest having the rights to the patent of the regenerative circuit.
That same year, he also broadcasted the first radio advertisement and presidential election report via his own radio station. He continued to broadcast radio shows, but found that he was unable to get the necessary financial backing.
In 1922, De Forest developed the Phonofilm process. The process was a new method of recording sound for movies, accomplished by recording sound directly onto the film in the form of two parallel lines. Although Hollywood initially ignored his invention, it later became the standard in movie production and he was credited with the invention of sound recording for motion pictures.
In 1931, he sold a radio manufacturing firm that he had owned to RCA. In 1946, De Forest was awarded the Edison Medal of the American Institute of Electrical Engineers for the invention of the triode. In 1959, he received an Academy Award for "pioneering inventions which brought sound to the motion picture" and was also given a star on the Hollywood Walk of Fame.
Lee De Forest died on June 30, 1961 in Hollywood and was buried in Los Angeles.