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Audion Receiver
An audion receiver makes use of a single vacuum tube or transistor to detect and amplify signals. It is so called because it originally used the audion tube as the active element. Unlike a crystal detector or Fleming valve detector, the audion provided amplification of the signal as well as detection. The audion was invented by Lee De Forest. In its operation, the circuit demodulates the radio frequency (RF) signal by rectification or square-law detection, and then amplifies this demodulated signal. The capacitor in series with the grid and parallel resistance forms a grid-leak detector which allow the grid to cathode to be used as a diode. In 1915 Edwin Armstrong developed an improved "regenerative" form of audion receiver that used the same vacuum tube for RF amplification, RF detection, and audio amplification.Derek K. Shaeffer, Thomas H. Lee, ''The design and implementation of low-power CMOS radio receivers'', Springer, 1999 {{ISBN, 0-7923-8518-7 page 6 See also * Tune ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vacuum Tube
A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric voltage, potential difference has been applied. The type known as a thermionic tube or thermionic valve utilizes thermionic emission of electrons from a hot cathode for fundamental electronic functions such as signal amplifier, amplification and current rectifier, rectification. Non-thermionic types such as a vacuum phototube, however, achieve electron emission through the photoelectric effect, and are used for such purposes as the detection of light intensities. 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 (i.e. Fleming valve), invented in 1904 by John Ambrose Fleming, contains only a heated electron-emitting cathode and an anode. Electrons can only flow in one direction through the device—fro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transistor
upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch electrical signals and electrical power, power. The transistor is one of the basic building blocks of modern electronics. It is composed of semiconductor material, usually with at least three terminals for connection to an electronic circuit. A voltage or current applied to one pair of the transistor's terminals controls the current through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal. Some transistors are packaged individually, but many more are found embedded in integrated circuits. Austro-Hungarian physicist Julius Edgar Lilienfeld proposed the concept of a field-effect transistor in 1926, but it was not possible to actually co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Audion Tube
The Audion was an electronic detecting or amplifying vacuum tube invented by American electrical engineer Lee de Forest in 1906.De Forest patented a number of variations of his detector tubes starting in 1906. The patent that most clearly covers the Audion is , Space Telegraphy', filed January 29, 1907, issued February 18, 1908 The link is to a reprint of the paper in the ''Scientific American Supplement'', Nos. 1665 and 1666, November 30, 1907 and December 7, 1907, p.348-350 and 354-356. It was the first triode, consisting of an evacuated glass tube containing three electrodes: a heated filament, a grid, and a plate. It is important in the history of technology because it was the first widely used electronic device which could amplify. A low power signal at the grid could control much more power in the plate circuit. Audions had more residual gas than later vacuum tubes; the residual gas limited the dynamic range and gave the Audion non-linear characteristics and erratic pe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crystal Detector
A crystal detector is an obsolete electronic component used in some early 20th century radio receivers that consists of a piece of crystalline mineral which rectifies the alternating current radio signal. It was employed as a detector ( demodulator) to extract the audio modulation signal from the modulated carrier, to produce the sound in the earphones. It was the first type of semiconductor diode, and one of the first semiconductor electronic devices. The most common type was the so-called cat's whisker detector, which consisted of a piece of crystalline mineral, usually galena (lead sulfide), with a fine wire touching its surface. Greenleaf Whittier Pickard, ''Detector for Wireless Telegraphy and Telephony'', filed: 21 June 1911, granted: 21 July 1914 The "asymmetric conduction" of electric current across electrical contacts between a crystal and a metal was discovered in 1874 by Karl Ferdinand Braun. Crystals were first used as radio wave detectors in 1894 by Jaga ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fleming Valve
The Fleming valve, also called the Fleming oscillation valve, was a thermionic valve or vacuum tube invented in 1904 by English physicist John Ambrose Fleming as a detector for early radio receivers used in electromagnetic wireless telegraphy. It was the first practical vacuum tube and the first thermionic diode, a vacuum tube whose purpose is to conduct current in one direction and block current flowing in the opposite direction. The thermionic diode was later widely used as a rectifier — a device which converts alternating current (AC) into direct current (DC) — in the power supplies of a wide range of electronic devices, until beginning to be replaced by the selenium rectifier in the early 1930s and almost completely replaced by the semiconductor diode in the 1960s. The Fleming valve was the forerunner of all vacuum tubes, which dominated electronics for 50 years. The IEEE has described it as "one of the most important developments in the history of electronics", and i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lee De Forest
Lee de Forest (August 26, 1873 – June 30, 1961) was an American inventor and a fundamentally important early pioneer in electronics. He invented the first electronic device for controlling current flow; the three-element " Audion" triode vacuum tube in 1906. This started the Electronic Age, and enabled the development of the electronic amplifier and oscillator. These made radio broadcasting and long distance telephone lines possible, and led to the development of talking motion pictures, among countless other applications. He had over 300 patents worldwide, but also a tumultuous career— he boasted that he made, then lost, four fortunes. He was also involved in several major patent lawsuits, spent a substantial part of his income on legal bills, and was even tried (and acquitted) for mail fraud. Despite this, he was recognised for his pioneering work with the 1922 IEEE Medal of Honor, the 1923 Franklin Institute Elliott Cresson Medal and the 1946 American Instit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vacuum Tube Audion
A vacuum is a space devoid of matter. The word is derived from the Latin adjective ''vacuus'' for "vacant" or "void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often discuss ideal test results that would occur in a ''perfect'' vacuum, which they sometimes simply call "vacuum" or free space, and use the term partial vacuum to refer to an actual imperfect vacuum as one might have in a laboratory or in space. In engineering and applied physics on the other hand, vacuum refers to any space in which the pressure is considerably lower than atmospheric pressure. The Latin term ''in vacuo'' is used to describe an object that is surrounded by a vacuum. The ''quality'' of a partial vacuum refers to how closely it approaches a perfect vacuum. Other things equal, lower gas pressure means higher-quality vacuum. For example, a typical vacuum cleaner produces enough suction to reduce air pressure by around 20%. But high ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Square-law Detector
In electronic signal processing Signal processing is an electrical engineering subfield that focuses on analyzing, modifying and synthesizing '' signals'', such as sound, images, and scientific measurements. Signal processing techniques are used to optimize transmissions, ..., a square law detector is a device that produces an output proportional to the square of some input.''IEEE Std. 100 Authoritative Dictionary of Standards Terms Seventh Edition'', IEEE, 2000, ,''Square law detection'' For example, in demodulating radio signals, a semiconductor diode can be used as a square law detector, providing an output current proportional to the square of the amplitude of the input voltage over some range of input amplitudes. A square law detector provides an output directly proportional to the power of the input electrical signal. References {{Signal-processing-stub Signal processing ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Grid-leak Detector
A grid leak detector is an electronic circuit that demodulates an amplitude modulated alternating current and amplifies the recovered modulating voltage. The circuit utilizes the non-linear cathode to control grid conduction characteristic and the amplification factor of a vacuum tube.H. A. Robinson, "The Operating Characteristics of Vacuum Tube Detectors", Part I, '' QST'', vol. XIV, no. 8, p. 23, Aug. 1930 Invented by Lee De Forest around 1912, it was used as the detector (demodulator) in the first vacuum tube radio receivers until the 1930s. History Early applications of triode tubes (''Audions'') as detectors usually did not include a resistor in the grid circuit. First use of a resistance in the grid circuit of a vacuum tube detector circuit may have been by Sewall Cabot in 1906. Cabot wrote that he made a pencil mark to discharge the grid condenser, after finding that touching the grid terminal of the tube would cause the detector to resume operation after having stopp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diode
A diode is a two- terminal electronic component that conducts current primarily in one direction (asymmetric conductance); it has low (ideally zero) resistance in one direction, and high (ideally infinite) resistance in the other. A diode vacuum tube or thermionic diode is a vacuum tube with two electrodes, a heated cathode and a plate, in which electrons can flow in only one direction, from cathode to plate. A semiconductor diode, the most commonly used type today, is a crystalline piece of semiconductor material with a p–n junction connected to two electrical terminals. Semiconductor diodes were the first semiconductor electronic devices. The discovery of asymmetric electrical conduction across the contact between a crystalline mineral and a metal was made by German physicist Ferdinand Braun in 1874. Today, most diodes are made of silicon, but other semiconducting materials such as gallium arsenide and germanium are also used. Among many uses, diodes are found ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Edwin Howard Armstrong
Edwin Howard Armstrong (December 18, 1890 – February 1, 1954) was an American electrical engineer and inventor, who developed FM (frequency modulation) radio and the superheterodyne receiver system. He held 42 patents and received numerous awards, including the first Medal of Honor awarded by the Institute of Radio Engineers (now IEEE), the French Legion of Honor, the 1941 Franklin Medal and the 1942 Edison Medal. He was inducted into the National Inventors Hall of Fame and included in the International Telecommunication Union's roster of great inventors. Armstrong attended Columbia University, and served as a professor there for most of his life. Early life Armstrong was born in the Chelsea district of New York City, the oldest of John and Emily (née Smith) Armstrong's three children. His father began working at a young age at the American branch of the Oxford University Press, which published bibles and standard classical works, eventually advancing to the positio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tuned Radio Frequency Receiver
A tuned radio frequency receiver (or TRF receiver) is a type of radio receiver that is composed of one or more tuned radio frequency (RF) amplifier stages followed by a detector ( demodulator) circuit to extract the audio signal and usually an audio frequency amplifier. This type of receiver was popular in the 1920s. Early examples could be tedious to operate because when tuning in a station each stage had to be individually adjusted to the station's frequency, but later models had ganged tuning, the tuning mechanisms of all stages being linked together, and operated by just one control knob. By the mid 1930s, it was replaced by the superheterodyne receiver patented by Edwin Armstrong. Background The TRF receiver was patented in 1916 by Ernst Alexanderson. His concept was that each stage would amplify the desired signal while reducing the interfering ones. Multiple stages of RF amplification would make the radio more sensitive to weak stations, and the multiple tuned cir ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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