Vacuum tube diodes

Thermionic Diode Vacuum tube that permits current to flow in only one direction, also called a vacuum tube diode. 

Modem electronic devices build on a long history of invention, discovery, and basic scientific research. The most critical devices are the control circuit elements — the diode and the switching devices. The latter began as triode vacuum tubes and are now generally transistors. Diodes pass current easily in only one direction. The original diode was invented in 1905 by J. Ambrose Flemming based on observations made in the laboratories of Edison Electric. This diode vacuum tube contained a hot filament, which emits electrons, and a metallic plate collector. Electrons flow only from filament to collector. The following year Lee DeForest created the triode vacuum tube and the electronic revolution was launched. 

Electronic Vacuum Tube. In special electronic vacuum diode tubes, with spacing between the cathode and anode of 10 )J.m, high gas concentrations of some types are beneficial to the operation of the tube under proper control. 

The vacuum-tube diode, invented by Fleming24 in 1904 [2,3], works because of the relative geometrical shapes of the two concentric electrodes, the cathode and the anode. It consists of a cylindrical glass enclosure that is partially evacuated, bonded, and sealed to a metal base. It contains an inner metallic thin-wire "cathode" (negative electrode, consisting of W, oxide-covered W, or a Th-W alloy), placed along the cylinder axis. This cathode is electrically heated to 900 K or above, using an auxiliary filament circuit, typically driven by a 6.3-V power supply, to foster thermoionic emission of electrons from the cathode. This cathode is cylindrically surrounded by a metallic outer electrode, the anode or "positive electrode" or "plate," which is a hollow metallic cylinder, whose axis coincides with that of the cathode. The... 

To recapitulate, a vacuum-tube diode works in part because of its geometry (any electron leaving the wire cathode and traversing the space-charge region can easily hit the plate that surrounds the cathode cylindrically, while few electrons leaving the plate are likely to hit the cathode) and in part because of temperature (the cathode is heated, the anode is not). 

Forward bias" means that the plate is kept at a large positive accelerating potential Ep > 0, which is similar to the positive bias in a vacuum-tube diode. The potential Ep applied to the plate is traditionally called the "B+" potential, obtained from the positive terminal (battery +) of a DC power supply or battery therefore Ep is also called /,. 

The first pn junction diode or rectifier was reported in 1949 [13]. The term "diode" comes from the vacuum-tube literature, and the new device was called a rectifier when it was used in electrical rectifier circuits. However, the term "diode" should be reserved to vacuum-tube devices, and "rectifiers" should be used for semiconductor pn junction devices. 

A schematic of an ESR spectrometer is shown in Fig. 3 more detailed discussion of construction and operation of the instrument can be found in Ref. 1 and in the citations therein, as well as in the manuals accompanying the spectrometer to be used. The microwave source is a vacuum-tube Klystron or a solid-state Gunn diode, which provides... 

Walter Haus Schottky (1886-1976) received his doctorate in physics under Max Planck from the Humboldt University in Berlin in 1912. Although his thesis was on the special theory of relativity, Schottky spent his life s work in the area of semiconductor physics. He alternated between industrial and academic positions in Germany for several years. He was with Siemens AG until 1919 and the University of Wurzburg from 1920 to 1923. From 1923 to 1927, Schottky was professor of theoretical physics at the University of Rostock. He rejoined Siemens in 1927, where he finished out his career. Schottky s inventions include the ribbon microphone, the superheterodyne radio receiver, and the tetrode vacuum tube. In 1929, he published Thermodynamik, a book on the thermodynamics of solids. Schottky and Wagner studied the statistical thermodynamics of point defect formation. The cation/anion vacancy pair in ionic solids is named the Schottky defect. In 1938, he produced a barrier layer theory to explain the rectifying behavior of metal-semiconductor contacts. Metal-semiconductor diodes are now called Schottky barrier diodes. 

The modern electronics era began at Bell Telephone Laboratories in 1948 with the invention of the solid-state transistor, which replaced the large thermionic vacuum tube, the mainstay of the electronics industry for the previous 40 years. Transistors were smaller and much more robust than their vacuum tube counterparts and required much less power to operate. Electronic circuits of the 1950s and early 1960s were assembled from discrete transistors, diodes, and resistors, for example, but rapid advances in circuit complexity and density, driven by developments in computer technology, soon led to an impasse, namely, how to approach the problem of interconnecting hundreds, perhaps thousands, (some visionaries would have said millions) of discrete devices into a complex circuit. 

A vacuum tube which contains only. anode (cold) and cathode (heated), but no grid is known as Tico Electrode Electron Tube or Diode, Such. a cube can be used to rectify alternating current... 

Following the invention of the transistor, for many years, they were made as individual, discrete electronic components and were connected to other electronic components (resistors, capacitors, inductors, diodes, etc.) on printed circuit boards to make an electronic circuit. The transistor s small size and low power consumption made it an ideal candidate to replace the bulky vacuum tubes then used to amplify electrical signals and switch electrical currents. These beneficial attributes of transistors made it possible for them to be used in making ever more complex electronic circuits in place of vacuum tubes. However, it did not take long before the limits of this approach of building circuits were reached. Circuits... 

Frequently dc generators have been used as sources of dc energy however, ac sources may be used and rectified by vacuum tube rectifier circuits or by use of high-current solid state diodes. A rectifier circuit for producing dc energy from an ac source is shown in Figure 5-7. The inductance in the primary circuit is a variable core reactor for current control. Numerous variations of this basic circuit are commercially available. A dc source such... 

Any other form of internally generated noise must depend upon bias. Since they add (quadratically) to Johnson noise, all other types of noise are referred to as excess noise. Three principal forms of excess noise exist. One amenable to analysis which is found in photoconductors is generation-recombination or g — r noise. A second, also amenable to analysis, which is found in photodiodes, i.e., p - n junctions and Schottky barrier diodes, is referred to as shot noise of diffusing carriers, or simply as shot noise. The third form of excess noise, not amenable to exact analysis, is called l//(one over/) noise because it exhibits a 1// power law spectrum to a close approximation. It has also been called flicker noise, a term carried over from a similar power law form of noise in vacuum tubes. 

A. Types of Element. Rectifiers are devices that allow the passage of current in only one direction. Thermionic emission of electrons, for example, is a one-way process and was the basis for vacuum-tube diodes. The cathode must be held negative with respect to the collector in order for electrons to flow. This explains the use of the word valve to describe what has been known in the United States as a tube. ... 

A diode is perhaps the first semiconductor circuit element that a student learns about in electronics courses, though most early diodes were constructed using vacuum tubes. It is very simplistic in structure, and basic diodes are very simple to connect in circuits. They have only two terminals, a cathode and an anode. The very name diode was created by British physicist William Henry Eccles in 1919 to describe the circuit element as having only the two terminals, one in and one out. 

As the electronics and the radio communication industries developed, it became apparent that there would be a need for human-made diodes to replace the natural crystals that were used in a trial-and-error manner. Two development paths were followed solid-state diodes and vacuum tube diodes. By the middle of the twentieth century, inexpensive germanium-based diodes had been developed as solid-state devices. The problem with solid-state diodes was that they lacked the ability to handle large currents, so for high-current applications, vacuum tube diodes, or thermionic diodes, were developed. In the twenty-first century, most diodes are semiconductor devices, with thermionic diodes existing only for the rare very high-power applications. 

Solid-State Diodes. Thermionic diodes, or vacuum tube diodes, tend to be large and consume a lot of electricity. However, paralleling the development of... 

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