A vacuum tube, also called a valve in British English, is an electronic device used in many older model radios, television sets, and amplifiers to control electric current flow. The cathode is heated, as in a light bulb, so it will emit electrons. This is called thermionic emission. The anode is the part that accepts the emitted electrons. The device may have other parts. Vacuum tubes must be hot to work. Most are made of glass, thus are fragile and can break. Vacuum tubes were used in the first computers like the ENIAC, which were large and need much work to continue operating.
Although the vacuum tube was invented by John Ambrose Fleming in 1904, it was Thomas Edison who discovered the \"Edison effect\" in 1883 which states that electricity does not necessarily need a solid material to move through; it can move through gas or vacuums as well.
John Ambrose Fleming invented the first vacuum tube, the diode, in 1904. Lee De Forest invented the \"audion\" in 1906 (which was improved by others as the triode in 1908) and used in the first telephone amplifiers. Many other kinds were invented for various purposes.
The transistor became cheaper in the 1960s and was much smaller, worked on lower voltages, and used less power. In addition, unlike vacuum tubes, they were much less likely to be damaged by being dropped and had extremely long life. Eventually, they were also much cheaper than glass vacuum tubes. At this time, most radios, television sets, and amplifiers began using transistors instead.  High powered electronics such as broadcasting transmitters were transistorized more slowly. Television receivers continued using the cathode ray tube until the mid-2000s.
In the 21st century, vacuum tubes are rarely used in common electronic equipment. Many devices today rely on the transistor over the vacuum tube. Some devices that still use the vacuum tube, however, include:
Edison's discovery that current can travel through a vacuum didn't turn out to be very useful information until 1904. That's when a British scientist named John A. Fleming made a vacuum tube known today as a diode. Then the diode was known as a \"valve,\" because it forced current in the tube to travel exclusively in one direction. Getting that single directional flow was critical for radio sets which needed to turn alternating current into direct current. The vacuum tube didn't reach its full maturity until Lee De Forest came along a decade later. De Forest invented something he called the \"audion.\" Not only did it force current to move in a single direction, but it could be used to increase the current along the way. De Forest put a metal grid in the middle of the vacuum tube. By using a small input current to change the voltage on the grid, De Forest could control the flow of a second, more powerful current, through the tube. The strength of two currents was not necessarily related -- a weak current might be applied to the tube's grid, but a much stronger current could come out the main electrodes of the tube. Turning weak currents into strong currents was crucial for a number of new technologies at that time. Bell Labs made use of it for its coast to coast phone system and vacuum tubes soon found their way into everything from hearing aids to radios to televisions. Sources -Crystal Fire
By using vacuum tubes instead of mechanical relays, computers could move away from mechanical switching and speed up switching on and off the flow of electrons. Vacuum tubes were also used in radios, televisions, radar equipment, and telephone systems during the first half of the 1900s.
In the 1950s, the invention of the transistor started to replace the vacuum tube, as vacuum tubes were larger, fragile like a light bulb, and expensive. As computing devices started to become smaller in size, transistors were more ideal to use due to their smaller size.
An electron tube (also known as a 'Vacuum tube', or a 'Valve' ) is a glass or metal enclosure in which electrons move through the vacuum or gas from one metal electrode to another. The vacuum tube is often used to amplify weak currents or act as a one-way valve (rectifier) for electric current.
In the 1950's and 1960's, television and radio repairs were often done by what is termed \" Tube Jockeys\". Other slang for vacuum tubes were \"Bottles\". Another slang phrase around vacuum tubes that was on air was the \"Gassy 807\", a double meaning to mean an 807 model tube that had lost its vacuum - or a glass of beer.
Some of these tube metallic structures were housed within one glass envelope, a space saving design. There was another type of vacuum tube structure used, and that was the Nuvistor. The Nuvistor had UHF applications and exhibited lower noise figures in vacuum tube amplifiers - heavily application dependent, and in audio applications problems with microphony with these types is a huge problem. In RF applications their low inter-electrode capacitances and good noise figures made them moderately common in the better FM tuners and VHF/UHF band radio communications equipment and test equipment. The nuvistor was mostly contrcated as a triode.
There is also a class of vacuum tube known as fast wave devices, and these are characterised by the phase velocity of the resonant wave having speeds greater than the speed of light. They operate at the high microwave frequency bands up to visible light. Specifically these are the:
Vacuum Tube / Thermionic Valves Includes: Basics How does a tube work Vacuum tube electrodes Diode valve / tube Triode Tetrode Beam Tetrode Pentode Equivalents Pin connections Numbering systems Valve sockets / bases Travelling wave tube Vacuum tube or thermionic valve technology has been in use since just after the beginning of the twentieth century.
The first observations of what eventually developed into vacuum tube or thermionic valve technology were observed by Edison. In his quest to manufacture better incandescent light bulbs, he noticed and effect that was later called the Edison Effect.
The next major development occurred when Lee de Forest added a third electrode called a grid. This opened up the basic thermionic valve or vacuum tube idea to amplify signals and provide considerably more functionality.
The first vacuum tube / thermionic valve was developed when Ambrose Fleming used a discovery Edison had made that was called the Edison Effect. Edison had not been able to find any applications for it, but Fleming used this two electrode diode it to rectify radio signals. Later Lee de Forest added a third electrode to make a triode. Further developments improved performance and added additional electrodes.
The concept of thermionic valve or vacuum tubes used the idea that a heated element in a vacuum emitted electrons that would normally remain in the vicinity of this heated element because of the charge attraction.
If a second electrode was placed into the vacuum and a high positive potential placed on it, then the electrons would be attracted away from the heated element towards this element with a high potential. As a result a current would flow in this direction.
The various different types of vacuum tube / thermionic valve enable a variety of different functions to be provided by these devices. Diodes are obviously very different to triodes, etc, but the other types of valve can be used in different circuits as required by the different applications.
Itis well known that editor of Enjoy the Music.com Steven R. Rochlin was good friends with editor of Vacuum Tube Valley Charlie Kittleson were good friends over the years. Vacuum Tube Valley(VTV) was a magazine produced by Charlie 'C.K.' Kittleson for the DIY and tube enthusiast.The publication spanned many years; producing 20 issues in total packed full of excellent information about audio vacuum tubes, vacuum tube equipment and a variety of DIY projects. Sadly, Charlie Kittleson passed away on February 10, 2009.
Vacuum tube and Transistor are types electronic switching devices used a variety of electronic devices and circuits such as computers, communication systems, power supplies, TV, radios, amplifiers, etc. However, both are significantly different from each other based on their technology and operation.
A vacuum tube is an electronic device used to control the current flowing in a circuit using a vacuum in a sealed glass tube. Basically, function wise the vacuum tube is an older version of modern transistor.
The practical example of a vacuum is the cathode ray tube (CRT) that was used in early television and computer monitors. An English physicist John Ambrose Fleming was invented the vacuum tube in 1904 which was a basic switching component of all electronic devices at that age.
A vacuum tube consists of two electrodes namely a cathode and an anode, which are enclosed in a sealed glass tube with all the air removed, i.e., there is vacuum inside the tube. The cathode produces electrons and the anode collects these electrons when a potential difference is applied to it. One major disadvantage of the vacuum tube is that it requires a heating element to produce electrons, due to which it consumes much amount of power and burns out quickly.
Both vacuum tubes and transistors perform almost the same function. The most significant difference between a vacuum tube and a transistor is that a vacuum tube is used in high-power applications while a transistor is used in low-power applications.
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