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| {{for|data diodes|Unidirectional network}}{{for|other uses|Diodes (disambiguation)}}
| | Hello my new friends.I have been writing since I was ten years old, and getting published since I was seventeen! I have always been a very positive person and was many years from the radio as an On-Air Personality! Speaking was an easy thing for me to begin doing, and my positive influence on others lead me to being a self-help writer and motivational speaker!<br><br>Nothing but the writing examples explain writer best. Feasible while selecting someone, may do ask for writing examples and after evaluating, purchase select the one you think can work as perfect in order to pen out your thoughts.<br><br><br><br>If you're unsure about anything at all, please remember must. When you know exactly exactly what the job is, not only can you receive it done faster, but you'll eliminate procrastination, often stems from uncertainty.<br><br>SERPs are "search engine result texte." These are the web pages that look at right after entering a phrase on looking engine. So, if you search for, say, "SEO Writing Services," the page notice after and also "enter" button is a SERP. In own a website, you have all the interest in being found by people who search for the products/services/information you offer. Therefore, truly make involving SEO tactics to strengthen your pages' visibility on search engines.<br><br>You will have the replacement of the add "AdSense" ads. These are the "Ads by Google" that view everywhere on other online websites. What happens will be the fact every page on your site will have these ads and when visitors click, then could collect revenue.<br><br>You have some outline or plan before purchasing a freelance writer. This is important so that crashes easier for that person to the writing when they could fully exactly what you need. This could help you buy the best freelance playwright.<br><br>The alternative involves deciding which leads you in order to follow through to. Right away you may notice that a few aren't worth period. For example in preserving the instance of finding prospects for your freelance writing business, is definitely the to bypass those trying for free articles. You can do this.<br><br>Just like educators and healthcare workers continually attend classes to earn their "Continuing Education Units," I invest money in acquiring the best books I will find to make my [http://help-forums.adobe.com/home/users/ims/4853/ims-4853248D53F5544E0A4C98C6@AdobeID/profile.form.html/content/adobeforums/en/user/profile/view/ writing] efforts more effective than my competition. On the other hand don't just read and reread them, I study them and apply what I've learned in everything I do. |
| [[Image:Diode-closeup.jpg|thumb|right|Closeup of a diode, showing the square shaped semiconductor crystal ''(black object on left)''.]]
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| [[Image:Dioden2.jpg|thumb|right|Various semiconductor diodes. Bottom: A [[bridge rectifier]]. In most diodes, a white or black painted band identifies the [[cathode]] terminal, that is, the terminal that positive charge ([[conventional current]]) will flow out of when the diode is conducting.<ref name="Tooley">{{cite book
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| | last = Tooley
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| | first = Mike
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| | title = Electronic Circuits: Fundamentals and Applications, 3rd Ed.
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| | publisher = Routlege
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| | year = 2012
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| | page = 81
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| | url = http://books.google.com/books?id=NunPn6R__TAC&pg=PA81
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| | isbn = 1-136-40731-6}}</ref><ref name="Lowe">{{cite web
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| | last = Lowe
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| | first = Doug
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| | title = Electronics Components: Diodes
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| | work = Electronics All-In-One Desk Reference For Dummies
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| | publisher = John Wiley & Sons
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| | year = 2013
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| | url = http://www.dummies.com/how-to/content/electronics-components-diodes.html
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| | accessdate = January 4, 2013}}</ref><ref name="Crecraft">{{cite book
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| | last = Crecraft
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| | first = David
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| | coauthors = Stephen Gergely
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| | title = Analog Electronics: Circuits, Systems and Signal Processing
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| | publisher = Butterworth-Heinemann
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| | year = 2002
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| | page = 110
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| | url = http://books.google.com/?id=lS7qN6iHyBYC&pg=PA110
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| | isbn = 0-7506-5095-8}}</ref><ref name="Horowitz">{{cite book
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| | last = Horowitz
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| | first = Paul
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| | coauthors = Winfield Hill
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| | title = The Art of Electronics, 2nd Ed.
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| | publisher = Cambridge University Press
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| | year = 1989
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| | location = London
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| | page = 44
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| | url = http://books.google.com/books?id=bkOMDgwFA28C&pg=PA44
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| | isbn = 0-521-37095-7}}</ref>]]
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| [[Image:Diode tube schematic.svg|thumb|right|Structure of a [[vacuum tube]] diode. The filament may be bare, or more commonly (as shown here), embedded within and insulated from an enclosing cathode]]
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| In [[electronics]], a '''diode''' is a two-[[Terminal (electronics)|terminal]] [[electronic component]] with asymmetric [[electrical conductance|conductance]], it has low (ideally zero) [[electrical resistance and conductance|resistance]] to current flow in one direction, and high (ideally [[Infinity|infinite]]) resistance in the other. A '''semiconductor diode''', the most common type today, is a [[crystalline]] piece of [[semiconductor]] material with a [[p–n junction]] connected to two electrical terminals.<ref>{{cite web|url=http://www.element-14.com/community/docs/DOC-22519/l/physical-explanation--general-semiconductors |title=Physical Explanation – General Semiconductors |date=2010-05-25 |accessdate=2010-08-06}}</ref> A [[vacuum tube]] diode has two [[electrode]]s, a [[Plate electrode|plate]] (anode) and a [[hot cathode|heated cathode]]. Semiconductor diodes were the first [[Semiconductor device|semiconductor electronic devices]]. The discovery of [[crystal]]s' [[Rectification (electricity)|rectifying]] abilities was made by German physicist [[Ferdinand Braun]] in 1874. The first semiconductor diodes, called [[cat's whisker diode]]s, developed around 1906, were made of mineral crystals such as [[galena]]. Today most diodes are made of [[silicon]], but other [[semiconductor]]s such as [[selenium]] or [[germanium]] are sometimes used.<ref>{{cite web|url=http://www.element-14.com/community/docs/DOC-22518/l/the-constituents-of-semiconductor-components |title=The Constituents of Semiconductor Components |date=2010-05-25 |accessdate=2010-08-06}}</ref>
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| ==Main functions==
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| The most common function of a diode is to allow an electric current to pass in one direction (called the diode's ''forward'' direction), while blocking current in the opposite direction (the ''reverse'' direction). Thus, the diode can be viewed as an electronic version of a [[check valve]]. This unidirectional behavior is called [[rectification (electricity)|rectification]], and is used to convert [[alternating current]] to [[direct current]], including extraction of [[modulation]] from radio signals in radio receivers—these diodes are forms of [[rectifier]]s.
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| However, diodes can have more complicated behavior than this simple on–off action, due to their [[linear circuit|nonlinear]] current-voltage characteristics. Semiconductor diodes begin conducting electricity only if a certain threshold voltage or cut-in voltage is present in the forward direction (a state in which the diode is said to be ''[[p–n junction#Forward bias|forward-biased]]''). The voltage drop across a forward-biased diode varies only a little with the current, and is a function of temperature; this effect can be used as a [[#Temperature measurements|temperature sensor]] or [[voltage reference]].
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| Semiconductor diodes' current–voltage characteristic can be tailored by varying the [[semiconductor materials]] and [[doping (semiconductor)|doping]], introducing impurities into the materials. These are exploited in special-purpose diodes that perform many different functions. For example, diodes are used to regulate voltage ([[Zener diode]]s), to protect circuits from high voltage surges ([[avalanche diode]]s), to electronically tune radio and TV receivers ([[varactor diode]]s), to generate [[radio frequency]] [[oscillation]]s ([[tunnel diode]]s, [[Gunn diode]]s, [[IMPATT diode]]s), and to produce light ([[light emitting diode]]s). Tunnel diodes exhibit [[negative resistance]], which makes them useful in some types of circuits.
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| ==History==
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| Thermionic ([[vacuum tube]]) diodes and [[solid state (electronics)|solid state]] (semiconductor) diodes were developed separately, at approximately the same time, in the early 1900s, as radio receiver [[detector (radio)|detector]]s. Until the 1950s [[vacuum tube]] diodes were more often used in radios because the early point-contact type semiconductor diodes ([[cat's-whisker detector]]s) were less stable, and because most receiving sets had vacuum tubes for amplification that could easily have diodes included in the tube (for example the [[12SQ7]] [[Vacuum duo-diode triode|double-diode triode]]), and vacuum tube rectifiers and gas-filled rectifiers handled some high voltage/high current rectification tasks beyond the capabilities of semiconductor diodes (such as [[metal rectifier|selenium rectifiers]]) available at the time.
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| ===Vacuum tube diodes===
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| {{further2|[[Vacuum tube#History and development|Vacuum tube]]}}
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| In 1873, [[Frederick Guthrie]] discovered the basic principle of operation of thermionic diodes.<ref>Frederick Guthrie (October 1873) [http://books.google.com/books?id=U08wAAAAIAAJ&pg=PA257#v=onepage&q&f=false "On a relation between heat and static electricity,"] ''The London, Edinburgh and Dublin Philosophical Magazine and Journal of Science'', 4th series, '''46''' : 257-266.</ref><ref>[http://nobelprize.org/physics/laureates/1928/richardson-lecture.pdf 1928 Nobel Lecture:] Owen W. Richardson, "Thermionic phenomena and the laws which govern them", December 12, 1929</ref> Guthrie discovered that a positively charged [[electroscope]] could be discharged by bringing a [[Ground (electricity)|grounded]] piece of white-hot metal close to it (but not actually touching it). The same did not apply to a negatively charged electroscope, indicating that the current flow was only possible in one direction.
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| [[Thomas Edison]] independently rediscovered the principle on February 13, 1880. At the time, Edison was investigating why the filaments of his carbon-filament light bulbs nearly always burned out at the positive-connected end. He had a special bulb made with a metal plate sealed into the glass envelope. Using this device, he confirmed that an invisible current flowed from the glowing filament through the [[vacuum]] to the metal plate, but only when the plate was connected to the positive supply.
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| Edison devised a circuit where his modified light bulb effectively replaced the resistor in a [[direct current|DC]] [[voltmeter]]. Edison was awarded a patent for this invention in 1884.<ref>Thomas A. Edison "Electrical Meter" {{US patent|307030}} Issue date: Oct 21, 1884</ref> Since there was no apparent practical use for such a device at the time, the patent application was most likely simply a precaution in case someone else did find a use for the so-called [[Edison effect]].
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| About 20 years later, [[John Ambrose Fleming]] (scientific adviser to the [[Marconi Company]]
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| and former Edison employee) realized that the Edison effect could be used as a precision [[Detector (radio)|radio detector]]. Fleming patented the first true thermionic diode, the [[Fleming valve]], in Britain on November 16, 1904<ref>{{cite web|url=http://www.jmargolin.com/history/trans.htm |title=Road to the Transistor |publisher=Jmargolin.com |date= |accessdate=2008-09-22}}</ref> (followed by {{US patent|803684}} in November 1905).
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| ===Solid-state diodes===
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| In 1874 German scientist [[Karl Ferdinand Braun]] discovered the "unilateral conduction" of crystals.<ref>Ferdinand Braun (1874) [http://gallica.bnf.fr/ark:/12148/bpt6k152378/f580.image.langEN "Ueber die Stromleitung durch Schwefelmetalle"] (On current conduction in metal sulphides), ''Annalen der Physik und Chemie'', '''153''' : 556-563.</ref><ref>[http://web.archive.org/web/20060211010305/http://chem.ch.huji.ac.il/~eugeniik/history/braun.htm Karl Ferdinand Braun]. chem.ch.huji.ac.il</ref> Braun patented the crystal rectifier in 1899.<ref>{{cite web|url=http://encyclobeamia.solarbotics.net/articles/diode.html |title=Diode |publisher=Encyclobeamia.solarbotics.net}}</ref> [[Copper(I) oxide|Copper oxide]] and [[selenium rectifier]]s were developed for power applications in the 1930s.
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| Indian scientist [[Jagadish Chandra Bose]] was the first to use a crystal for detecting radio waves in 1894. <ref name="Sarkar">{{Cite book | last = Sarkar | first = Tapan K. | title = History of wireless | publisher = John Wiley and Sons | year = 2006 | location = USA | pages = 94, 291–308 | url = http://books.google.com/books?id=NBLEAA6QKYkC&pg=PA291 | isbn = 0-471-71814-9}}</ref> The [[crystal detector]] was developed into a practical device for [[wireless telegraphy]] by [[Greenleaf Whittier Pickard]], who invented a [[silicon]] crystal detector in 1903 and received a patent for it on November 20, 1906.<ref>Pickard, Greenleaf Whittier "Means for receiving intelligence communicated by electric waves" {{US patent|836531}} Issued: August 30, 1906</ref> Other experimenters tried a variety of other substances, of which the most widely used was the mineral [[galena]] ([[Galena|lead sulfide]]). Other substances offered slightly better performance, but galena was most widely used because it had the advantage of being cheap and easy to obtain. The crystal detector in these early [[crystal radio]] sets consisted of an adjustable wire point-contact (the so-called "cat's whisker"), which could be manually moved over the face of the crystal in order to obtain optimum signal. This troublesome device was superseded by thermionic diodes by the 1920s, but after high purity semiconductor materials became available, the crystal detector returned to dominant use with the advent of inexpensive fixed-[[germanium]] diodes in the 1950s. [[Bell Labs]] also developed a germanium diode for microwave reception, and AT&T used these in their microwave towers that criss-crossed the nation starting in the late 1940s, carrying telephone and network television signals. [[Bell Labs]] did not develop a satisfactory thermionic diode for microwave reception.
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| ===Etymology===
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| At the time of their invention, such devices were known as [[rectifier]]s. In 1919, the year [[tetrode]]s were invented, [[William Henry Eccles]] coined the term '''''diode''''' from the [[Greek and Latin roots|Greek roots]] ''di'' (from ''δί''), meaning "two", and ''ode'' (from ''ὁδός''), meaning "path". (However, the word ''diode'' itself, as well as ''[[triode]], [[tetrode]], [[penthode]], [[hexode]]'', was already in use as a term of [[Time-division multiplexing|multiplex]] [[telegraphy]]; see, for example, ''The telegraphic journal and electrical review'', September 10, 1886, p. 252).
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| ====Rectifiers====
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| {{Main|Rectifier}}
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| Although all diodes ''rectify'', the term '[[rectifier]]' is normally reserved for higher currents and voltages than would normally be found in the rectification of lower power [[Signal (electrical engineering)|signals]]; examples include:
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| * [[Power supply]] rectifiers (''[[Half-wave rectifier#Half-wave rectification|half-wave]]'', ''full-wave'', ''[[Bridge rectifiers|bridge]]'')
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| * [[Flyback diode]]s
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| ==Thermionic diodes==
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| [[Image:Diode-english-text.svg|thumb|left|Diode vacuum tube construction]]
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| [[Image:Vacuum diode.svg|thumb|110px|right|The symbol for an indirect heated vacuum-tube diode. From top to bottom, the components are the anode, the cathode, and the heater filament.]]
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| A thermionic diode is a [[thermionic valve|thermionic-valve]] device (also known as a [[vacuum tube]], tube, or valve), consisting of a sealed evacuated glass envelope containing two [[electrode]]s: a [[thermionic cathode|cathode]] heated by a [[electrical filament|filament]], and a [[plate electrode|plate]] ([[anode]]). Early examples were fairly similar in appearance to [[incandescent light bulb]]s.
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| In operation, a separate current through the filament (heater), a high resistance wire made of [[nichrome]], heats the cathode red hot (800–1000 °C), causing it to release [[electron]]s into the vacuum, a process called [[thermionic emission]]. The cathode is coated with [[oxide]]s of [[alkaline earth metal]]s such as [[barium]] and [[strontium]] [[oxide]]s, which have a low [[work function]], to increase the number of electrons emitted. (Some valves use ''direct heating'', in which a tungsten filament acts as both heater and cathode.) The alternating voltage to be rectified is applied between the cathode and the concentric plate electrode. When the plate has a positive voltage with respect to the cathode, it [[electrostatics|electrostatically]] attracts the electrons from the cathode, so a current of electrons flows through the tube from cathode to plate. However when the polarity is reversed and the plate has a negative voltage, no current flows, because the cathode electrons are not attracted to it. The unheated plate does not emit any electrons itself. So current can only flow through the tube in one direction, from cathode to plate.
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| In a [[mercury-arc valve]], an arc forms between a refractory conductive anode and a pool of liquid mercury acting as cathode. Such units were made with ratings up to hundreds of kilowatts, and were important in the development of [[High-voltage direct current|HVDC]] power transmission. Some types of smaller thermionic rectifiers sometimes had mercury vapor fill to reduce their forward voltage drop and to increase current rating over thermionic hard-vacuum devices.
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| Throughout the vacuum tube era, valve diodes were used in analog signal applications and as rectifiers in DC power supplies in consumer electronics such as radios, televisions, and sound systems. They were replaced in power supplies beginning in the 1940s by [[selenium rectifier]]s and then by semiconductor diodes by the 1960s. Today they are still used in a few high power applications where their ability to withstand transients and their robustness gives them an advantage over semiconductor devices. The recent (2012) resurgence of interest among [[audiophile]]s and recording studios in old valve audio gear such as [[guitar amplifier]]s and home audio systems has provided a market for the legacy consumer diode valves.
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| ==Semiconductor diodes==<!-- This section is linked from [[Boltzmann constant]] -->
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| ===Electronic symbols===
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| {{Main|Electronic symbol}}
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| The symbol used for a semiconductor diode in a [[circuit diagram]] specifies the type of diode. There are alternate symbols for some types of diodes, though the differences are minor.
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| <gallery>
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| Image:Diode symbol.svg|Diode
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| Image:LED symbol.svg|[[Light-emitting diode|Light Emitting Diode]] (LED)
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| Image:Photodiode symbol.svg|[[w:Photodiode|Photodiode]]
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| Image:Schottky diode symbol.svg|[[w:Schottky diode|Schottky diode]]
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| Image:Transient voltage suppression diode symbol.svg|[[Transient-voltage-suppression diode|Transient Voltage Suppression]] (TVS)
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| Image:Tunnel diode symbol.svg|[[Tunnel diode]]
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| Image:Varicap symbol.svg|[[w:Varicap|Varicap]]
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| Image:Zener_diode_symbol.svg|[[Zener diode]]
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| Image:Diode pinout en fr.svg|Typical diode packages in same alignment as diode symbol. Thin bar depicts the [[cathode]].
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| </gallery>
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| ===Point-contact diodes===
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| A '''point-contact diode''' works the same as the junction diodes described below, but their construction is simpler. A block of n-type semiconductor is built, and a conducting sharp-point contact made with some group-3 metal is placed in contact with the semiconductor. Some metal migrates into the semiconductor to make a small region of p-type semiconductor near the contact. The long-popular 1N34 germanium version is still used in radio receivers as a detector and occasionally in specialized analog electronics.
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| ===Junction diodes===
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| Most diodes today are silicon junction diodes. A junction is formed between the p and n regions which is also called a depletion region.
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| ====p–n junction diode====
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| {{main|p–n diode}}
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| A p–n junction diode is made of a crystal of [[semiconductor]]. Impurities are added to it to create a region on one side that contains negative [[charge carrier]]s (electrons), called [[n-type semiconductor]], and a region on the other side that contains positive charge carriers ([[Electron hole|holes]]), called [[p-type semiconductor]]. When two materials i.e. n-type and p-type are attached together, a momentary flow of electrons occur from n to p side resulting in a third region where no charge carriers are present. It is called Depletion region due to the absence of charge carriers (electrons and holes in this case). The diode's terminals are attached to each of these regions. The boundary between these two regions, called a [[p–n junction]], is where the action of the diode takes place. The crystal allows electrons to flow from the N-type side (called the [[cathode]]) to the P-type side (called the [[anode]]), but not in the opposite direction.
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| ====Schottky diode====
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| {{main|Schottky diode}}
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| Another type of junction diode, the [[Schottky diode]], is formed from a [[metal–semiconductor junction]] rather than a p–n junction, which reduces capacitance and increases switching speed.
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| ===Current–voltage characteristic===
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| [[File:Diode_current_wiki.png|thumb|400px|I–V (current vs. voltage) characteristics of a p–n junction diode]]
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| A semiconductor diode's behavior in a circuit is given by its [[current–voltage characteristic]], or I–V graph (see graph below). The shape of the curve is determined by the transport of charge carriers through the so-called ''[[depletion zone|depletion layer]]'' or ''[[depletion region]]'' that exists at the [[p–n junction]] between differing semiconductors. When a p–n junction is first created, conduction-band (mobile) electrons from the N-[[dopant|doped]] region diffuse into the P-[[dopant|doped]] region where there is a large population of holes (vacant places for electrons) with which the electrons "recombine". When a mobile electron recombines with a hole, both hole and electron vanish, leaving behind an immobile positively charged donor (dopant) on the N side and negatively charged acceptor (dopant) on the P side. The region around the p–n junction becomes depleted of [[charge carrier]]s and thus behaves as an [[nonconductor|insulator]].
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| However, the width of the depletion region (called the [[depletion width]]) cannot grow without limit. For each [[electron–hole pair]] that recombines, a positively charged [[dopant]] ion is left behind in the N-doped region, and a negatively charged dopant ion is left behind in the P-doped region. As recombination proceeds more ions are created, an increasing electric field develops through the depletion zone that acts to slow and then finally stop recombination. At this point, there is a "built-in" potential across the depletion zone.
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| If an external voltage is placed across the diode with the same polarity as the built-in potential, the depletion zone continues to act as an insulator, preventing any significant electric current flow (unless [[electron–hole pair]]s are actively being created in the junction by, for instance, light; see [[photodiode]]). This is the ''[[Reverse bias|reverse bias]]'' phenomenon. However, if the polarity of the external voltage opposes the built-in potential, recombination can once again proceed, resulting in substantial electric current through the p–n junction (i.e. substantial numbers of electrons and holes recombine at the junction). For silicon diodes, the built-in potential is approximately 0.7 V (0.3 V for Germanium and 0.2 V for Schottky). Thus, if an external current passes through the diode, the voltage across the diode increases logarithmic with the current such that the P-doped region is positive with respect to the N-doped region and the diode is said to be "turned on" as it has a ''[[p–n junction#Forward bias|forward bias]]''. The diode is commonly said to have a forward "threshold" voltage, which it conducts above and is cutoff below. However, this is only an approximation as the forward characteristic is according to the Shockley equation absolutely smooth (see graph below).
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| A diode's [[I–V characteristic]] can be approximated by four regions of operation.
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| At very large reverse bias, beyond the [[Peak Inverse Voltage|peak inverse voltage]] or PIV, a process called reverse [[avalanche breakdown|breakdown]] occurs that causes a large increase in current (i.e., a large number of electrons and holes are created at, and move away from the p–n junction) that usually damages the device permanently. The [[avalanche diode]] is deliberately designed for use in the avalanche region. In the [[Zener diode]], the concept of PIV is not applicable. A Zener diode contains a heavily doped p–n junction allowing electrons to tunnel from the valence band of the p-type material to the conduction band of the n-type material, such that the reverse voltage is "clamped" to a known value (called the ''Zener voltage''), and avalanche does not occur. Both devices, however, do have a limit to the maximum current and power in the clamped reverse-voltage region. Also, following the end of forward conduction in any diode, there is reverse current for a short time. The device does not attain its full blocking capability until the reverse current ceases.
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| The second region, at reverse biases more positive than the PIV, has only a very small reverse saturation current. In the reverse bias region for a normal P–N rectifier diode, the current through the device is very low (in the µA range). However, this is temperature dependent, and at sufficiently high temperatures, a substantial amount of reverse current can be observed (mA or more).
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| The third region is forward but small bias, where only a small forward current is conducted.
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| The current–voltage curve is [[Exponential function|exponential]]. In a smal silicon diode at rated currents, the voltage drop is about 0.6 to 0.7 [[volt]]s. The value is different for other diode types—[[Schottky diode]]s can be rated as low as 0.2 V, Germanium diodes 0.25 to 0.3 V, and red or blue [[light-emitting diode]]s (LEDs) can have values of 1.4 V and 4.0 V respectively.<ref>citation needed</ref>
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| At higher currents the forward voltage drop of the diode increases. A drop of 1 V to 1.5 V is typical at full rated current for power diodes.
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| ===Shockley diode equation===
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| The ''Shockley ideal diode equation'' or the ''diode law'' (named after [[transistor]] co-inventor [[William Shockley|William Bradford Shockley]]) gives the I–V characteristic of an ideal diode in either forward or reverse bias (or no bias). The ''Shockley ideal diode equation'' is below, where n, the ideality factor, is equal to 1 :
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| :<math>I=I_\mathrm{S} \left( e^{V_\mathrm{D}/(n V_\mathrm{T})}-1 \right),\,</math>
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| where
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| :''I'' is the diode current,
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| :''I''<sub>S</sub> is the reverse bias [[saturation current]] (or scale current),
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| :''V''<sub>D</sub> is the voltage across the diode,
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| :''V''<sub>T</sub> is the [[thermal voltage]], and
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| :''n'' is the ''ideality factor'', also known as the ''quality factor'' or sometimes ''emission coefficient''. The ideality factor ''n'' typically varies from 1 to 2 (though can in some cases be higher), depending on the fabrication process and semiconductor material and in many cases is assumed to be approximately equal to 1 (thus the notation ''n'' is omitted). The ideality factor does not form part of the ''Shockley ideal diode equation'', and was added to account for imperfect junctions as observed in real transistors. By setting n = 1 above, the equation reduces to the ''Shockley ideal diode equation''.
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| The [[thermal voltage]] ''V''<sub>T</sub> is approximately 25.85 mV at 300 K, a temperature close to "room temperature" commonly used in device simulation software. At any temperature it is a known constant defined by:
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| :<math>V_\mathrm{T} = \frac{k T}{q} \, ,</math>
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| where ''k'' is the [[Boltzmann constant]], ''T'' is the absolute temperature of the p–n junction, and ''q'' is the magnitude of charge of an [[electron]] (the [[elementary charge]]).
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| The reverse saturation current, ''I''<sub>S</sub>, is not constant for a given device, but varies with temperature; usually more significantly than ''V''<sub>T</sub>, so that ''V''<sub>D</sub> typically decreases as ''T'' increases.
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| The ''Shockley ideal diode equation'' or the ''diode law'' is derived with the assumption that the only processes giving rise to the current in the diode are drift (due to electrical field), diffusion, and thermal [[carrier generation and recombination|recombination–generation]] (R–G) (this equation is derived by setting n = 1 above). It also assumes that the R–G current in the depletion region is insignificant. This means that the ''Shockley ideal diode equation'' doesn't account for the processes involved in reverse breakdown and photon-assisted R–G. Additionally, it doesn't describe the "leveling off" of the I–V curve at high forward bias due to internal resistance. Introducing the ideality factor, n, accounts for recombination and generation of carriers.
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| Under ''reverse bias'' voltages the exponential in the diode equation is negligible, and the current is a constant (negative) reverse current value of −''I<sub>S</sub>''. The reverse ''breakdown region'' is not modeled by the Shockley diode equation.
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| For even rather small ''forward bias'' voltages the exponential is very large because the thermal voltage is very small, so the subtracted '1' in the diode equation is negligible and the forward diode current is often approximated as
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| :<math>I=I_\mathrm{S} e^{V_\mathrm{D}/(n V_\mathrm{T})}</math>
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| The use of the diode equation in circuit problems is illustrated in the article on [[diode modelling#Shockley diode model|diode modeling]].
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| ===Small-signal behavior===
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| For circuit design, a small-signal model of the diode behavior often proves useful. A specific example of diode modeling is discussed in the article on [[small-signal model|small-signal circuits]].
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| ===Reverse-recovery effect===
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| Following the end of forward conduction in a p–n type diode, a reverse current flows for a short time. The device does not attain its blocking capability until the mobile charge in the junction is depleted.
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| The effect can be significant when switching large currents very quickly.<ref>[http://ecee.colorado.edu/~ecen5817/hw/hw1/Diode%20reverse%20recovery%20in%20a%20boost%20converter.pdf Diode reverse recovery in a boost converter]. ECEN5817. ecee.colorado.edu</ref> A certain amount of "reverse recovery time" t<sub>r</sub> (on the order of tens of nanoseconds to a few microseconds) may be required to remove the reverse recovery charge Q<sub>r</sub> from the diode. During this recovery time, the diode can actually conduct in the reverse direction. <!-- That is to say, current will effectively flow from the cathode to the anode! --> In certain real-world cases it can be important to consider the losses incurred by this non-ideal diode effect.<ref>[http://ecee.colorado.edu/~ecen5797/course_material/SwLossSlides.pdf Inclusion of Switching Loss in the Averaged Equivalent Circuit Model]. ECEN5797. ecee.colorado.edu</ref> However, when the [[slew rate]] of the current is not so severe (e.g. Line frequency) the effect can be safely ignored. For most applications, the effect is also negligible for [[Schottky diode]]s.
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| The reverse current ceases abruptly when the stored charge is depleted; this abrupt stop is exploited in [[step recovery diode]]s for generation of extremely short pulses.
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| ==Types of semiconductor diode==
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| [[Image:Diodes.jpg|right|thumb|Several types of diodes. The scale is centimeters.]]
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| [[Image:DO-41 Dimensions.svg|right|thumb|150px|Typical datasheet drawing showing the dimensions of a DO-41 diode package]]
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| There are several types of [[p–n diode|p–n junction diode]]s, which emphasize either a different physical aspect of a diode often by geometric scaling, doping level, choosing the right electrodes, are just an application of a diode in a special circuit, or are really different devices like the Gunn and laser diode and the [[MOSFET]]:
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| Normal (p–n) diodes, which operate as described above, are usually made of doped [[silicon]] or, more rarely, [[germanium]]. Before the development of silicon power rectifier diodes, [[cuprous oxide]] and later [[selenium]] was used; its low efficiency gave it a much higher forward voltage drop (typically 1.4 to 1.7 V per "cell", with multiple cells stacked to increase the peak inverse voltage rating in high voltage rectifiers), and required a large heat sink (often an extension of the diode's metal [[Substrate (semiconductor)|substrate]]), much larger than a silicon diode of the same current ratings would require. The vast majority of all diodes are the p–n diodes found in [[CMOS]] [[integrated circuits]], which include two diodes per pin and many other internal diodes.
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| [[Avalanche diode]]s
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| :These are diodes that conduct in the reverse direction when the reverse bias voltage exceeds the breakdown voltage. These are electrically very similar to Zener diodes (and are often mistakenly called Zener diodes), but break down by a different mechanism: the ''avalanche effect''. This occurs when the reverse electric field across the p–n junction causes a wave of ionization, reminiscent of an avalanche, leading to a large current. Avalanche diodes are designed to break down at a well-defined reverse voltage without being destroyed. The difference between the avalanche diode (which has a reverse breakdown above about 6.2 V) and the Zener is that the channel length of the former exceeds the mean free path of the electrons, so there are collisions between them on the way out. The only practical difference is that the two types have temperature coefficients of opposite polarities.
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| [[Cat's whisker diode|Cat's whisker or crystal diodes]]
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| :These are a type of point-contact diode. The cat's whisker diode consists of a thin or sharpened metal wire pressed against a semiconducting crystal, typically [[galena]] or a piece of [[coal]]. The wire forms the anode and the crystal forms the cathode. Cat's whisker diodes were also called crystal diodes and found application in [[crystal radio receiver]]s. Cat's whisker diodes are generally obsolete, but may be available from a few manufacturers.{{Citation needed|date=June 2009}}
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| [[Constant current diode]]s
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| :These are actually [[JFET]]s<ref>[http://digikey.com/Web%20Export/Supplier%20Content/Vishay_8026/PDF/Vishay_CurrentRegulatorDiodes.pdf Current regulator diodes]. Digikey.com (2009-05-27). Retrieved on 2013-12-19.</ref> with the gate shorted to the source, and function like a two-terminal current-limiting analog to the voltage-limiting Zener diode. They allow a current through them to rise to a certain value, and then level off at a specific value. Also called ''CLDs'', ''constant-current diodes'', ''diode-connected transistors'', or ''current-regulating diodes''.
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| [[Esaki]] or [[tunnel diode]]s
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| :These have a region of operation showing [[negative resistance]] caused by [[quantum tunneling]],<ref>{{cite journal|author=Jonscher, A. K. |doi=10.1088/0508-3443/12/12/304|title=The physics of the tunnel diode|year=1961|journal=British Journal of Applied Physics|volume=12|issue=12|page=654}}</ref> allowing amplification of signals and very simple bistable circuits. Due to the high carrier concentration, tunnel diodes are very fast, may be used at low (mK) temperatures, high magnetic fields, and in high radiation environments.<ref>{{cite journal|author=Dowdey, J. E., and Travis, C. M. |doi= 10.1109/TNS2.1964.4315475|title=An Analysis of Steady-State Nuclear Radiation Damage of Tunnel Diodes|year=1964|journal=IEEE Transactions on Nuclear Science|volume=11|issue=5|page=55}}</ref> Because of these properties, they are often used in spacecraft.
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| [[Gunn diode]]s
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| :These are similar to tunnel diodes in that they are made of materials such as GaAs or InP that exhibit a region of [[negative resistance|negative differential resistance]]. With appropriate biasing, dipole domains form and travel across the diode, allowing high frequency [[microwave]] [[electronic oscillator|oscillators]] to be built.
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| [[Light-emitting diode]]s (LEDs)
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| :In a diode formed from a [[Direct bandgap|direct band-gap]] semiconductor, such as [[gallium arsenide]], carriers that cross the junction emit [[photon]]s when they recombine with the majority carrier on the other side. Depending on the material, [[wavelength]]s (or colors)<ref>[http://digikey.com/Web%20Export/Supplier%20Content/Vishay_8026/PDF/Vishay_ClassificationOfComponents.pdf Classification of components]. Digikey.com (2009-05-27). Retrieved on 2013-12-19.</ref> from the [[infrared]] to the near [[ultraviolet]] may be produced.<ref>{{cite web|url=http://www.element-14.com/community/docs/DOC-22517/l/component-construction--vishay-optoelectronics |title=Component Construction|date=2010-05-25 |accessdate=2010-08-06}}</ref> The forward potential of these diodes depends on the wavelength of the emitted photons: 2.1 V corresponds to red, 4.0 V to violet. The first LEDs were red and yellow, and higher-frequency diodes have been developed over time. All LEDs produce incoherent, narrow-spectrum light; "white" LEDs are actually combinations of three LEDs of a different color, or a blue LED with a yellow [[scintillator]] coating. LEDs can also be used as low-efficiency photodiodes in signal applications. An LED may be paired with a photodiode or phototransistor in the same package, to form an [[opto-isolator]].
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| [[Laser diode]]s
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| :When an LED-like structure is contained in a [[optical cavity|resonant cavity]] formed by polishing the parallel end faces, a [[laser]] can be formed. Laser diodes are commonly used in [[optical storage]] devices and for high speed [[optical communication]].
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| [[Thermal diode]]s
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| :This term is used both for conventional p–n diodes used to monitor temperature due to their varying forward voltage with temperature, and for [[Peltier–Seebeck effect|Peltier heat pumps]] for [[thermoelectric cooling|thermoelectric heating and cooling]]. Peltier heat pumps may be made from semiconductor, though they do not have any rectifying junctions, they use the differing behaviour of charge carriers in N and P type semiconductor to move heat.
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| [[Photodiode]]s
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| :All semiconductors are subject to optical [[charge carrier]] generation. This is typically an undesired effect, so most semiconductors are packaged in light blocking material. Photodiodes are intended to sense light([[photodetector]]), so they are packaged in materials that allow light to pass, and are usually PIN (the kind of diode most sensitive to light).<ref>[http://digikey.com/Web%20Export/Supplier%20Content/Vishay_8026/PDF/Vishay_ComponentConstruction.pdf Component Construction]. Digikey.com (2009-05-27). Retrieved on 2013-12-19.</ref> A photodiode can be used in [[solar cell]]s, in [[photometry (optics)|photometry]], or in [[optical communication]]s. Multiple photodiodes may be packaged in a single device, either as a linear array or as a two-dimensional array. These arrays should not be confused with [[charge-coupled device]]s.
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| [[PIN diode]]s
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| :A PIN diode has a central un-doped, or ''intrinsic'', layer, forming a p-type/intrinsic/n-type structure.<ref>{{cite web|url=http://www.element-14.com/community/docs/DOC-22516/l/physics-and-technology--vishay-optoelectronics |title=Physics and Technology|date=2010-05-25 |accessdate=2010-08-06}}</ref> They are used as radio frequency switches and attenuators. They are also used as large-volume, ionizing-radiation detectors and as [[photodetector]]s. PIN diodes are also used in [[power electronics]], as their central layer can withstand high voltages. Furthermore, the PIN structure can be found in many [[power semiconductor device]]s, such as [[IGBT]]s, power [[MOSFET]]s, and [[thyristor]]s.
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| [[Schottky diode]]s
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| :[[Walter H. Schottky|Schottky]] diodes are constructed from a metal to semiconductor contact. They have a lower forward voltage drop than p–n junction diodes. Their forward voltage drop at forward currents of about 1 mA is in the range 0.15 V to 0.45 V, which makes them useful in voltage [[Clamper (electronics)|clamping applications]] and prevention of transistor saturation. They can also be used as low loss [[rectifier]]s, although their reverse leakage current is in general higher than that of other diodes. Schottky diodes are [[majority carrier]] devices and so do not suffer from minority carrier storage problems that slow down many other diodes—so they have a faster reverse recovery than p–n junction diodes. They also tend to have much lower junction capacitance than p–n diodes, which provides for high switching speeds and their use in high-speed circuitry and RF devices such as [[switched-mode power supply]], [[Frequency mixer|mixer]]s, and [[Detector (radio)|detectors]].
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| Super barrier diodes
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| :Super barrier diodes are rectifier diodes that incorporate the low forward voltage drop of the Schottky diode with the surge-handling capability and low reverse leakage current of a normal p–n junction diode.
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| [[Gold]]-doped diodes
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| :As a dopant, gold (or [[platinum]]) acts as recombination centers, which helps a fast recombination of minority carriers. This allows the diode to operate at signal frequencies, at the expense of a higher forward voltage drop. Gold-doped diodes are faster than other p–n diodes (but not as fast as Schottky diodes). They also have less reverse-current leakage than Schottky diodes (but not as good as other p–n diodes).<ref>[http://www.ixyspower.com/images/technical_support/Application%20Notes%20By%20Topic/FREDs,%20Schottky%20and%20GaAS%20Diodes/IXAN0044.pdf Fast Recovery Epitaxial Diodes (FRED) Characteristics – Applications – Examples]. (PDF) . Retrieved on 2013-12-19.</ref><ref>Sze, S. M. ''Modern Semiconductor Device Physics'', Wiley Interscience, ISBN 0-471-15237-4</ref> A typical example is the 1N914.
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| Snap-off or [[Step recovery diode]]s
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| : The term ''step recovery'' relates to the form of the reverse recovery characteristic of these devices. After a forward current has been passing in an [[Step recovery diode|SRD]] and the current is interrupted or reversed, the reverse conduction will cease very abruptly (as in a step waveform). SRDs can, therefore, provide very fast voltage transitions by the very sudden disappearance of the charge carriers.
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| [[Stabistor]]s or ''Forward Reference Diodes''
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| : The term ''stabistor'' refers to a special type of diodes featuring extremely stable [[p–n junction#Forward bias|forward voltage]] characteristics. These devices are specially designed for low-voltage stabilization applications requiring a guaranteed voltage over a wide current range and highly stable over temperature.
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| [[Transient voltage suppression diode]] (TVS)
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| :These are avalanche diodes designed specifically to protect other semiconductor devices from high-voltage [[Transient (oscillation)|transients]].<ref>[http://digikey.com/Web%20Export/Supplier%20Content/Vishay_8026/PDF/Vishay_ProtectingLowCurrentLoads.pdf Protecting Low Current Loads in Harsh Electrical Environments]. Digikey.com (2009-05-27). Retrieved on 2013-12-19.</ref> Their p–n junctions have a much larger cross-sectional area than those of a normal diode, allowing them to conduct large currents to ground without sustaining damage.
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| [[Varicap]] or varactor diodes
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| : These are used as voltage-controlled [[capacitors]]. These are important in PLL ([[phase-locked loop]]) and FLL ([[frequency-locked loop]]) circuits, allowing tuning circuits, such as those in television receivers, to lock quickly. They also enabled tunable oscillators in early discrete tuning of radios, where a cheap and stable, but fixed-frequency, crystal oscillator provided the reference frequency for a [[voltage-controlled oscillator]].
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| [[Zener diode]]s
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| :These can be made to conduct backward, and are correctly termed reverse breakdown diodes. This effect, called [[Zener breakdown]], occurs at a precisely defined voltage, allowing the diode to be used as a precision voltage reference. The term Zener diode is colloquially applied to several types of breakdown diodes, but strictly speaking Zener diodes have a breakdown voltage of below 5 volts, whilst those above that value are usually avalanche diodes. In practical voltage reference circuits, Zener and switching diodes are connected in series and opposite directions to balance the temperature coefficient to near-zero. Some devices labeled as high-voltage Zener diodes are actually avalanche diodes (see above). Two (equivalent) Zeners in series and in reverse order, in the same package, constitute a transient absorber (or [[Transorb]], a registered trademark). The Zener diode is named for Dr. [[Clarence Melvin Zener]] of Carnegie Mellon University, inventor of the device.
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| Other uses for semiconductor diodes include sensing temperature, and computing analog [[logarithm]]s (see [[Operational amplifier applications#Logarithmic_output]]).
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| ==Numbering and coding schemes==
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| There are a number of common, standard and manufacturer-driven numbering and coding schemes for diodes; the two most common being the [[Electronic Industries Alliance|EIA]]/[[JEDEC]] standard and the European [[Pro Electron]] standard:
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| ===EIA/JEDEC===
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| The standardized 1N-series numbering ''[[JEDEC#Origins|EIA370]]'' system was introduced in the US by EIA/JEDEC (Joint Electron Device Engineering Council) about 1960. Among the most popular in this series were: 1N34A/1N270 (Germanium signal), 1N914/1N4148 (Silicon signal), [[1N4001]]-1N4007 (Silicon 1A power rectifier) and 1N54xx (Silicon 3A power rectifier)<ref>{{cite web|url=http://www.jedec.org/Home/about_jedec.cfm |title=About JEDEC |publisher=Jedec.org |date= |accessdate=2008-09-22}}</ref><ref>{{cite web|url=http://news.elektroda.net/introduction-dates-of-common-transistors-and-diodes-t94332.html |title=EDAboard.com |publisher=News.elektroda.net |date=2010-06-10 |accessdate=2010-08-06}}</ref><ref>{{cite web|url=http://semiconductormuseum.com/Museum_Index.htm |title=Transistor Museum Construction Projects Point Contact Germanium Western Electric Vintage Historic Semiconductors Photos Alloy Junction Oral History |publisher=Semiconductormuseum.com |author=I.D.E.A |date= |accessdate=2008-09-22}}</ref>
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| ===JIS===
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| The [[JIS semiconductor designation]] system has all semiconductor diode designations starting with "1S".
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| ===Pro Electron===
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| The European [[Pro Electron]] coding system for [[active component]]s was introduced in 1966 and comprises two letters followed by the part code. The first letter represents the semiconductor material used for the component (A = Germanium and B = Silicon) and the second letter represents the general function of the part (for diodes: A = low-power/signal, B = Variable capacitance, X = Multiplier, Y = Rectifier and Z = Voltage reference), for example:
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| *AA-series germanium low-power/signal diodes (e.g.: AA119)
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| *BA-series silicon low-power/signal diodes (e.g.: BAT18 Silicon RF Switching Diode)
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| *BY-series silicon rectifier diodes (e.g.: BY127 1250V, 1A rectifier diode)
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| *BZ-series silicon Zener diodes (e.g.: BZY88C4V7 4.7V Zener diode)
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| Other common numbering / coding systems (generally manufacturer-driven) include:
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| *GD-series germanium diodes (e.g.: GD9){{spaced ndash}}this is a very old coding system
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| *OA-series germanium diodes (e.g.: OA47){{spaced ndash}}a [[Mullard–Philips tube designation|coding sequence]] developed by [[Mullard]], a UK company
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| As well as these common codes, many manufacturers or organisations have their own systems too{{spaced ndash}}for example:
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| *HP diode 1901-0044 = JEDEC 1N4148
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| *UK military diode CV448 = Mullard type OA81 = [[General Electric Company plc|GEC]] type GEX23
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| ==Related devices==
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| *[[Rectifier]]
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| *[[Transistor]]
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| *[[Thyristor]] or silicon controlled rectifier (SCR)
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| *[[TRIAC]]
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| *[[DIAC|Diac]]
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| *[[Varistor]]
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| In optics, an equivalent device for the diode but with laser light would be the [[Optical isolator]], also known as an Optical Diode, that allows light to only pass in one direction. It uses a [[Faraday rotator]] as the main component.
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| ==Applications==
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| ===Radio demodulation===
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| The first use for the diode was the demodulation of [[amplitude modulation|amplitude modulated]] (AM) radio broadcasts. The history of this discovery is treated in depth in the [[radio]] article. In summary, an AM signal consists of alternating positive and negative peaks of a radio carrier wave, whose [[amplitude]] or [[Envelope detector|envelope]] is proportional to the original audio signal. The diode (originally a crystal diode) [[rectifier|rectifies]] the AM radio frequency signal, leaving only the positive peaks of the carrier wave. The audio is then extracted from the rectified carrier wave using a simple [[electronic filter|filter]] and fed into an audio amplifier or [[transducer]], which generates sound waves.
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| ===Power conversion===
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| [[File:ACtoDCpowersupply.png|250px|thumb|Schematic of basic AC-to-DC power supply]]
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| [[Rectifier]]s are constructed from diodes, where they are used to convert [[alternating current]] (AC) electricity into [[direct current]] (DC). Automotive [[alternator (auto)|alternator]]s are a common example, where the diode, which rectifies the AC into DC, provides better performance than the [[Commutator (electric)|commutator]] or earlier, [[electrical generator|dynamo]]. Similarly, diodes are also used in ''[[Cockcroft-Walton generator|Cockcroft–Walton]] [[voltage multiplier]]s'' to convert AC into higher DC voltages.
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| ===Over-voltage protection===
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| Diodes are frequently used to conduct damaging high voltages away from sensitive electronic devices. They are usually reverse-biased (non-conducting) under normal circumstances. When the voltage rises above the normal range, the diodes become forward-biased (conducting). For example, diodes are used in ([[stepper motor]] and [[H-bridge]]) [[motor controller]] and [[relay]] circuits to de-energize coils rapidly without the damaging [[voltage spike]]s that would otherwise occur. (Any diode used in such an application is called a [[flyback diode]]). Many [[integrated circuits]] also incorporate diodes on the connection pins to prevent external voltages from damaging their sensitive [[transistors]]. Specialized diodes are used to protect from over-voltages at higher power (see [[#Types of semiconductor diode|Diode types]] above).
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| ===Logic gates===
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| Diodes can be combined with other components to construct [[logical conjunction|AND]] and [[logical disjunction|OR]] [[logic gate]]s. This is referred to as [[diode logic]].
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| ===Ionizing radiation detectors===
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| In addition to light, mentioned above, [[semiconductor]] diodes are sensitive to more [[energy|energetic]] radiation. In [[electronics]], [[cosmic ray]]s and other sources of ionizing radiation cause [[noise]] [[pulse]]s and single and multiple bit errors.
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| This effect is sometimes exploited by [[particle detector]]s to detect radiation. A single particle of radiation, with thousands or millions of [[electron volt]]s of energy, generates many charge carrier pairs, as its energy is deposited in the semiconductor material. If the depletion layer is large enough to catch the whole shower or to stop a heavy particle, a fairly accurate measurement of the particle's energy can be made, simply by measuring the charge conducted and without the complexity of a magnetic spectrometer, etc.
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| These semiconductor radiation detectors need efficient and uniform charge collection and low leakage current. They are often cooled by [[liquid nitrogen]]. For longer-range (about a centimetre) particles, they need a very large depletion depth and large area. For short-range particles, they need any contact or un-depleted semiconductor on at least one surface to be very thin. The back-bias voltages are near breakdown (around a thousand volts per centimetre). Germanium and silicon are common materials. Some of these detectors sense position as well as energy.
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| They have a finite life, especially when detecting heavy particles, because of radiation damage. Silicon and germanium are quite different in their ability to convert [[gamma ray]]s to electron showers.
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| [[Semiconductor detector]]s for high-energy particles are used in large numbers. Because of energy loss fluctuations, accurate measurement of the energy deposited is of less use.
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| ===Temperature measurements===
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| A diode can be used as a [[temperature]] measuring device, since the forward voltage drop across the diode depends on temperature, as in a [[silicon bandgap temperature sensor]]. From the Shockley ideal diode equation given above, it might ''appear'' that the voltage has a ''positive'' temperature coefficient (at a constant current), but usually the variation of the [[Saturation current|reverse saturation current]] term is more significant than the variation in the thermal voltage term. Most diodes therefore have a ''negative'' temperature coefficient, typically −2 mV/˚C for silicon diodes at room temperature. This is approximately linear for temperatures above about 20 [[kelvin]]s. Some graphs are given for 1N400x series,<ref>[http://www.cliftonlaboratories.com/1n400x_diode_family_forward_voltage.htm 1N400x Diode Family Forward Voltage]. Cliftonlaboratories.com. Retrieved on 2013-12-19.</ref> and CY7 cryogenic temperature sensor.<ref>[http://www.omega.com/Temperature/pdf/CY7.pdf Cryogenic Temperature Sensors]. omega.com</ref>
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| ===Current steering===
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| Diodes will prevent currents in unintended directions. To supply power to an electrical circuit during a power failure, the circuit can draw current from a [[Battery (electricity)|battery]]. An [[uninterruptible power supply]] may use diodes in this way to ensure that current is only drawn from the battery when necessary. Likewise, small boats typically have two circuits each with their own battery/batteries: one used for engine starting; one used for domestics. Normally, both are charged from a single alternator, and a heavy-duty split-charge diode is used to prevent the higher-charge battery (typically the engine battery) from discharging through the lower-charge battery when the alternator is not running.
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| Diodes are also used in [[electronic keyboards|electronic musical keyboards]]. To reduce the amount of wiring needed in electronic musical keyboards, these instruments often use [[keyboard matrix (music)|keyboard matrix]] circuits. The keyboard controller scans the rows and columns to determine which note the player has pressed. The problem with matrix circuits is that, when several notes are pressed at once, the current can flow backwards through the circuit and trigger "[[Keyboard (computing)#Control processor|phantom keys]]" that cause "ghost" notes to play. To avoid triggering unwanted notes, most keyboard matrix circuits have diodes soldered with the switch under each key of the [[musical keyboard]]. The same principle is also used for the switch matrix in solid-state [[pinball machine]]s.
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| ==Abbreviations==
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| Diodes are usually referred to as ''D'' for diode on [[printed circuit board|PCBs]]. Sometimes the abbreviation ''CR'' for ''crystal rectifier'' is used.<ref>{{cite book|author=John Ambrose Fleming|year=1919|url=http://books.google.com/?id=xHNBAAAAIAAJ&pg=PA550|title=The Principles of Electric Wave Telegraphy and Telephony|place=London|publisher=Longmans, Green|page=550}}</ref>
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| ==Two-terminal nonlinear devices==
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| Many other two-terminal nonlinear devices exist, for example a [[neon lamp]] has two terminals in a glass envelope and has interesting and useful nonlinear properties. Lamps including arc-discharge lamps, [[incandescent lamp]]s, [[fluorescent lamp]]s and [[mercury vapor lamp]]s have two terminals and display nonlinear current–voltage characteristics.
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| ==See also==
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| {{Portal|Electronics}}
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| *[[Active rectification]]
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| *[[Diode modelling]]
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| *[[wikt:junction diode|Junction diode]]
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| *[[Lambda diode]]
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| *[[p–n junction]]
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| *[[Small-signal model]]
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| ==References==
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| {{reflist|35em}}
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| ==External links==
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| {{Commons category|Diodes}}
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| * {{cite book |last1=Wintrich |first1= Arendt|last2= Nicolai|first2= Ulrich|last3= Tursky|first3= Werner|last4= Reimann|first4= Tobias|title= Application Manual 2011|url= http://www.powerguru.org/wordpress/wp-content/uploads/2012/12/SEMIKRON_application_manual_power_semiconductors.pdf |format=PDF|edition= 2nd|year= 2011|publisher= Semikron|location= Nuremberg|isbn= 978-3-938843-66-6}}
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| *[http://www.allaboutcircuits.com/vol_3/chpt_3/1.html Diodes and Rectifiers] – Chapter on All About Circuits
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| *[http://www.powerguru.org/structure-and-functional-behavior-of-pin-diodes/ Structure and Functional Behavior of PIN Diodes] – PowerGuru
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| ===Interactive and animations===
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| *[http://www-g.eng.cam.ac.uk/mmg/teaching/linearcircuits/diode.html Interactive Explanation of Semiconductor Diode], University of Cambridge
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| *[http://www.ee.byu.edu/cleanroom/schottky_animation.phtml Schottky Diode Flash Tutorial Animation]
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| {{Electronic component}}
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| [[Category:Diodes| ]]
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| {{Link FA|tt}}
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| {{Link FA|eo}}
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