1883, T. Edison, an American scientist who contributed more than 2,000 inventions to mankind, made a small experiment to find the best filament material for electric light bulbs. He installed a short piece of copper wire near the carbon wire inside the vacuum bulb, hoping that the copper wire could prevent the carbon wire from evaporating. Edison was disappointed with the experimental results, but inadvertently, he found that the copper wire that was not connected to the circuit produced a weak current because it received the hot electrons emitted by the carbon wire. Edison didn't pay attention to this phenomenon, just put it on record and declared a patent that didn't find any use. This is the so-called "Edison effect".
Edison himself ignored the "Edison effect" and shocked a young man on the other side of the ocean. 1885, Dr. J. Fleming, a 30-year-old British electrical engineer, insisted that it would definitely find practical use for thermionic vacuum emission. After repeated experiments, he finally found that if carbon wire and copper plate are installed in the vacuum bulb as cathode and shielding electrode respectively, the electrons in the bulb can flow in one direction. After many experiments, 1904, Fleming developed a special light bulb-"thermionic valve", which can be used as AC rectifier and radio detector, thus giving birth to the world's first electron tube, called vacuum diode.
However, it was not until the invention of vacuum triode that electron tubes became practical devices. The inventor of vacuum triode is American scientist Lee de forest (1873- 196 1).
De Forrester was born in Iowa, the midwestern United States,1August 26th, 873. When I was very young, my father moved to Alabama with his family, took over a bankrupt congregational school and lived a poor life. The local white community objected to his father taking black people to school and looked down on their families. Therefore, little De Forrest seldom associates with people and develops a relatively withdrawn character.
When I was a child, Deforest was not outstanding and was regarded as a mediocre child by the teacher. His only hobby is disassembling all kinds of mechanical gadgets, and his ambition is not great. He just wants to be a mechanic or mechanic. But he was quickly inspired by the rapid development of science and technology at the end of 19, and "invented" several small machines at the age of 13. Although his father hoped that his son would become a priest in the future, deforest secretly decided to make scientific research his lifelong goal. At the age of 20, he won a scholarship from Sheffield College of Science, Yale University. All his classmates call him "the most mediocre and neurotic student in the school". He seems to be interested in nothing but electricity, especially electromagnetic wave propagation. With few scholarships, deforest often has to work for others. 1899, finally got a doctorate in physics.
Originally, De Forrest should have stayed in the university to teach, but one thing changed his life forever.
It happened in the autumn of 1899, and deforest was writing his doctoral thesis "Reflection of Hertzian Waves at Two Ends of Parallel Conductor", which was probably the first paper involving radio in all American universities at that time. During this period, the annual international regatta will be held in new york, eclipsed by the visit of Italian radio inventor Marconi. The endless publicity of the New York Herald Tribune aroused the news that Marconi was going to give a radio performance.
Early that morning, Marconi boarded the warship moored in the port on time and sent back the news of the game by wireless telegram in time. For five hours, the New York Herald Tribune headquarters received more than 4,000 words of news reports from Marconi, which made American journalists open their eyes and marvel.
The audience pushed Marconi off the warship, and enthusiastic people invited Marconi, the "father of radio", to give them a live demonstration at the port. Deforest is naturally among the onlookers. He boldly walked behind Marconi and studied the radio equipment carefully. Marconi was affable and unreservedly explained the principle of radio transmitter to young students, and told him that the sensitivity of "metal chip detector" was too poor, which seriously affected the receiving and sending effect. It was this conversation with Marconi that made deforest set up his great ambition of invention and innovation.
After graduation, he first worked in the laboratory of Chicago West Electric Company, and soon invented the electrolytic detector and AC transmitter. 1902, he rented a shabby hut in Times Street, new york, and founded deforest wireless telegraph company, bent on inventing more advanced radio detection devices. At the same time, he will also show the prospect of radio application to the American public with his own invention.
Just when the research was not going well, the news that Fleming invented the vacuum diode came, which lit up his road like lightning. Foster couldn't sit still any longer. He trotted in the street, buying glass tubes, adding vacuum pumps, and looking for materials to make vacuum tubes. Think while running, until the data collection is completed, the design scheme is basically mature. He chose a platinum wire as the filament and installed a small piece of metal net near the filament. After the glass shell was vacuumized and electrified, he really "pursued" the trace of electrons.
However, after years of hard thinking, deforest is unwilling to stop this interesting experiment. He pondered for a while, suddenly grabbed a wire, bent it into a "Z" shape, and carefully installed it between the filament and the metal mesh. This wire can be used to receive electrons emitted from the filament at the same time, and it can also be used for other purposes. Little did he know that the small wire he installed would affect the development of electronic technology in the 20th century.
Deforest was extremely surprised to find that after putting the Z-shaped wire into a vacuum tube, as long as a weak variable voltage is applied to it, a larger variable current can be received on the metal screen, and the change rule is exactly the same-Deforest discovered the "amplification" effect of the vacuum tube. Later, he changed the wire into a metal mesh in the form of a fence, so that his electron tube had three "poles"-filament pole, screen pole and grid stage, in which the grid stage was responsible for controlling and amplifying electrical signals. 1907, deforest applied for the invention patent of vacuum triode (electron tube) to the US Patent Office.
However, because of the deception of partners, deforest's company closed down twice. 19 12 years, he was even innocently summoned by the federal court in new york, USA. Some people accused his company of selling overstocked products and engaging in commercial fraud. The stupid judge ruled that the vacuum tube invented by deforest was a "worthless glass tube".
19 12 years, under the pressure of imprisonment at any time, deforest came to Palo Alto, a small town near San Francisco, California, and made unremitting efforts to improve vacuum transistors. In the hut at No.913 Emerson Street, De Forrest connected several triodes, connected them to the telephone microphone and earphone, and then put his "ingersoll Watch" in front of the microphone. The ticking of the watch almost deafened his ears.
De Forrester's former residence in Palo Alto still stands a small commemorative plaque with a line written in the name of the municipal government: "Lee De Forrester discovered the amplification effect of electron tubes here." Commemorate the foundation laid by this great invention for the emerging electronic industry. This place has now grown into a world-famous Silicon Valley.
Deforest is a prolific inventor who obtained more than 300 patents in his life. In addition to electron tubes, his inventions include film edge recording technology, high-frequency electrothermal physiotherapy machine used in medicine and so on. He has repeatedly failed in business, and his technological inventions have not brought him any economic benefits. Many important patents were sold to AT&T at low prices. T), even the patent of electron tube amplifier only sold for $390,000. However, his invention also won him the titles of "father of radio", "father of television" and "father of electron tube".