Аудион: Бірінші триодтық электрондық құрылғының тарихы

Electronic detecting or amplifying vacuum tube

The Audion was an electronic detecting or amplifying vacuum tube Improved, it was patented as the first triode in 1908, consisting of an evacuated glass tube containing three electrodes: a heated filament (the cathode, made out of tantalum), a grid, and a plate (the anode). who used it to build the first amplifying radio receivers and electronic oscillators. The many practical applications for amplification motivated its rapid development, and the original Audion was superseded within a few years by improved versions with a higher vacuum. (right) Later design of an audion tube. The grid and plate are in two parts on either side of the central filament. In both these tubes the filament is burned out. De Forest was granted a patent for his early two electrode diode version of the Audion on November 13, 1906 , and the "triode" (three electrode) version was patented in 1908 De Forest continued to claim that he developed the Audion independently from John Ambrose Fleming's earlier research on the thermionic valve (for which Fleming received Great Britain patent 24850 and the American Fleming valve patent ), and de Forest became embroiled in many radio related patent disputes. De Forest was famous for saying that he "didn't know why it worked, it just did". He always referred to the vacuum triodes developed by other researchers as "Oscillaudions", although there is no evidence that he had any significant input to their development. It is true that after the invention of the true vacuum triode in 1913 (see below), de Forest continued to manufacture various types of radio transmitting and receiving apparatus, (examples of which are illustrated on this page). However, although he routinely described these devices as using "Audions", they actually used high vacuum triodes, using circuitry very similar to that developed by other experimenters. In 1914, Columbia University student Edwin Howard Armstrong worked with professor John Harold Morecroft to document the electrical principles of the Audion. Armstrong published his explanation of the Audion in Electrical World in December 1914, complete with circuit diagrams and oscilloscope graphs. In March and April 1915, Armstrong spoke to the Institute of Radio Engineers in New York and Boston, respectively, presenting his paper "Some Recent Developments in the Audion Receiver", which was published in September. The problem was that (possibly to distance his invention from the Fleming valve) de Forest's original patents specified that low pressure gas inside the Audion was essential to its operation (Audion being a contraction of "Audio Ion"), and in fact early Audions had severe reliability problems due to this gas being adsorbed by the metal electrodes. The Audions sometimes worked extremely well; at other times they would barely work at all. As well as de Forest himself, numerous researchers had tried to find ways to improve the reliability of the device by stabilizing the partial vacuum. Much of the research that led to the development of true vacuum tubes was carried out by Irving Langmuir in the General Electric (GE) research laboratories.

Langmuir had long suspected that certain assumed limitations on the performance of various low pressure and vacuum electrical devices, might not be fundamental physical limitations at all, but simply due to contamination and impurities in the manufacturing process. His first success was in demonstrating that, contrary to what Edison and others had long asserted, incandescent lamps could function more efficiently and with longer life if the glass envelope was filled with low pressure inert gas rather than a complete vacuum. However, this only worked if the gas used was meticulously 'scrubbed" of all traces of oxygen and water vapor. He then applied the same approach to producing a rectifier for the newly developed "Coolidge" X ray tubes. Again contrary to what had been widely believed to be possible, by virtue of meticulous cleanliness and attention to detail, he was able to produce versions of the Fleming Diode that could rectify hundreds of thousands of volts. His rectifiers were called "Kenotrons" from the Greek keno (empty, contains nothing, as in a vacuum) and tron (device, instrument). He then turned his attention to the Audion tube, again suspecting that its notoriously unpredictable behaviour might be tamed with more care in the manufacturing process. However he took a somewhat unorthodox approach. Instead of trying to stabilize the partial vacuum, he wondered if it was possible to make the Audion function with the total vacuum of a Kenotron, since that was somewhat easier to stabilize. He soon realized that his "vacuum" Audion had markedly different characteristics from the de Forest version, and was really a quite different device, capable of linear amplification and at much higher frequencies. To distinguish his device from the Audion he named it the "Pliotron", from the Greek plio (more or extra, in this sense meaning gain, more signal coming out than went in). Essentially, he referred to all his vacuum tube designs as Kenotrons, the Pliotron basically being a specialized type of Kenotron. However, because Pliotron and Kenotron were registered trademarks, technical writers tended to use the more generic term "vacuum tube". By the mid 1920s, the term "Kenotron" had come to exclusively refer to vacuum tube rectifiers, while the term "Pliotron" had fallen into disuse. Ironically, in popular usage, the sound alike brands "Radiotron" and "Ken Rad" outlasted the original names.