The groundwork laid by these scientists and inventors, however, was critical to the development of subsequent vacuum tube technology. Although thermionic emission was originally reported in 1873 by Frederick Guthrie, it was Thomas Edison's apparently independent discovery of the phenomenon in 1883 that became well known.
The groundwork laid by these scientists and inventors, however, was critical to the development of subsequent vacuum tube technology. Although thermionic emission was originally reported in 1873 by Frederick Guthrie, it was Thomas Edison's apparently independent discovery of the phenomenon in 1883 that became well known.
In both types, the electrons are accelerated from the cathode to the anode by the electric field in the tube. The simplest vacuum tube, the diode, invented in 1904 by John Ambrose Fleming, contains only a heated electron-emitting cathode and an anode.
In 1904, as a result of experiments conducted on Edison effect bulbs imported from the United States, he developed a device he called an "oscillation valve" (because it passes current in only one direction).
In 1906, Robert von Lieben filed for a patent for a cathode ray tube which included magnetic deflection.
It was only years later that John Ambrose Fleming utilized the rectifying property of the diode tube to detect (demodulate) radio signals, a substantial improvement on the early cat's-whisker detector already used for rectification. Amplification by vacuum tube became practical only with Lee De Forest's 1907 invention of the three-terminal "audion" tube, a crude form of what was to become the triode.
He would later help refine the triode vacuum tube. However, Lee De Forest is credited with inventing the triode tube in 1907 while experimenting to improve his original (diode) Audion.
In 1908, De Forest was granted a patent () for such a three-electrode version of his original Audion for use as an electronic amplifier in radio communications.
In 1912, De Forest brought the Audion to Harold Arnold in AT&T's engineering department.
Round invented the indirectly heated tube around 1913. The filaments require constant and often considerable power, even when amplifying signals at the microwatt level.
Arnold developed high-vacuum tubes which were tested in the summer of 1913 on AT&T's long-distance network.
The high-vacuum tubes could operate at high plate voltages without a blue glow. Finnish inventor Eric Tigerstedt significantly improved on the original triode design in 1914, while working on his sound-on-film process in Berlin, Germany.
Consequently, General Electric started producing hard vacuum triodes (which were branded Pliotrons) in 1915.
The development of the diffusion pump in 1915 and improvement by Irving Langmuir led to the development of high-vacuum tubes.
Langmuir patented the hard vacuum triode, but De Forest and AT&T successfully asserted priority and invalidated the patent. Pliotrons were closely followed by the French type 'TM' and later the English type 'R' which were in widespread use by the allied military by 1916.
Schottky invented the tetrode tube in 1919.
This technique was employed and led to the success of the Neutrodyne radio during the 1920s. However, neutralization required careful adjustment and proved unsatisfactory when used over a wide range of frequencies. ===Tetrodes and pentodes=== To combat the stability problems and limited voltage gain due to the Miller effect, the physicist Walter H.
This 1920s device has three triodes in a single glass envelope together with all the fixed capacitors and resistors required to make a complete radio receiver.
This two-grid tube is called a tetrode, meaning four active electrodes, and was common by 1926. However, the tetrode had one new problem.
The pentode was invented in 1926 by Bernard D.
In the 1930s, indirectly heated cathode tubes became widespread in equipment using AC power.
In 1934 Flowers built a successful experimental installation using over 3,000 tubes in small independent modules; when a tube failed, it was possible to switch off one module and keep the others going, thereby reducing the risk of another tube failure being caused; this installation was accepted by the Post Office (who operated telephone exchanges).
EMI engineers Cabot Bull and Sidney Rodda developed the design which became the 6L6, the first popular beam power tube, introduced by RCA in 1936 and later corresponding tubes in Europe the KT66, KT77 and KT88 made by the Marconi-Osram Valve subsidiary of GEC (the KT standing for "Kinkless Tetrode"). "Pentode operation" of beam power tubes is often described in manufacturers' handbooks and data sheets, resulting in some confusion in terminology.
In 1938 a technique was developed to use an all-glass construction with the pins fused in the glass base of the envelope.
Although some applications had used earlier technologies such as the spark gap transmitter for radio or mechanical computers for computing, it was the invention of the thermionic vacuum tube that made these technologies widespread and practical, and created the discipline of electronics. In the 1940s, the invention of semiconductor devices made it possible to produce solid-state devices, which are smaller, more efficient, reliable, durable, safer, and more economical than thermionic tubes.
This Emerson set also has a single tube socket, but because it uses a four-pin base, the additional element connections are made on a "mezzanine" platform at the top of the tube base. By 1940 multisection tubes had become commonplace.
Later work confirmed that tube unreliability was not as serious an issue as generally believed; the 1946 ENIAC, with over 17,000 tubes, had a tube failure (which took 15 minutes to locate) on average every two days.
High-purity nickel tubing and cathode coatings free of materials such as silicates and aluminum that can reduce emissivity also contribute to long cathode life. The first such "computer tube" was Sylvania's 7AK7 pentode of 1948 (these replaced the 7AD7, which was supposed to be better quality than the standard 6AG7 but proved too unreliable).
By the late 1950s, it was routine for special-quality small-signal tubes to last for hundreds of thousands of hours if operated conservatively.
Each Mk2 consumed 15 kilowatts; most of the power was for the tube heaters. A Colossus reconstruction was switched on in 1996; it was upgraded to Mk2 configuration in 2004; it found the key for a wartime German ciphertext in 2007. ====Whirlwind and "special-quality" tubes==== To meet the reliability requirements of the 1951 US digital computer Whirlwind, "special-quality" tubes with extended life, and a long-lasting cathode in particular, were produced.
The "acorn tube" (named due to its shape) was also very small, as was the metal-cased RCA nuvistor from 1959, about the size of a thimble.
While firmly established by history, the term "detector" is not of itself descriptive and should be considered outdated. Higher-power diode tubes or power rectifiers found their way into power supply applications until they were eventually replaced first by selenium, and later, by silicon rectifiers in the 1960s. ===Triodes=== Originally, the only use for tubes in radio circuits was for rectification, not amplification.
Each Mk2 consumed 15 kilowatts; most of the power was for the tube heaters. A Colossus reconstruction was switched on in 1996; it was upgraded to Mk2 configuration in 2004; it found the key for a wartime German ciphertext in 2007. ====Whirlwind and "special-quality" tubes==== To meet the reliability requirements of the 1951 US digital computer Whirlwind, "special-quality" tubes with extended life, and a long-lasting cathode in particular, were produced.
Each Mk2 consumed 15 kilowatts; most of the power was for the tube heaters. A Colossus reconstruction was switched on in 1996; it was upgraded to Mk2 configuration in 2004; it found the key for a wartime German ciphertext in 2007. ====Whirlwind and "special-quality" tubes==== To meet the reliability requirements of the 1951 US digital computer Whirlwind, "special-quality" tubes with extended life, and a long-lasting cathode in particular, were produced.
Each Mk2 consumed 15 kilowatts; most of the power was for the tube heaters. A Colossus reconstruction was switched on in 1996; it was upgraded to Mk2 configuration in 2004; it found the key for a wartime German ciphertext in 2007. ====Whirlwind and "special-quality" tubes==== To meet the reliability requirements of the 1951 US digital computer Whirlwind, "special-quality" tubes with extended life, and a long-lasting cathode in particular, were produced.
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