A diode is an electronic component of two directional terminals in one direction (asymmetric conductance); it has a low resistance (ideally zero) in one direction, and a high (ideally unlimited) resistance on the other. The vacuum tube diode uses electron thermionic emission and unidirectional conduction between the cathode and the plate. semiconductor Diodes, the most common type today, are the crystalline portion of a semiconductor material with a p-n connection connected to two electrical terminals. The semiconductor diode is the first semiconductor electronic device. The invention of asymmetric electrical conduction in contact between crystal and metal minerals was made by German physicist Ferdinand Braun in 1874. Today, most diodes are made of silicon, but other materials such as gallium arsenide and germanium are used.
Video Diode
Fungsi utama
The most common function of a diode is to allow an electric current to pass through one direction (called the forward direction of the diode), while blocking it in the opposite direction ( backwards direction). Thus, the diode can be viewed as an electronic version of the valve. This unidirectional behavior is called rectification, and is used to convert alternating current (AC) into direct current (dc). The rectifier form, diode can be used for tasks such as extracting modulation from radio signals in radio receivers.
However, the diode can have more complicated behavior than this simple on-off action, due to its nonlinear current voltage characteristics. The semiconductor diode begins to conduct electricity only if a certain threshold voltage or cut-in voltage is present in the forward direction (the state at which the diode is said to be forward biased ). The voltage drop across the forward biased diode varies only slightly with the current, and is a function of temperature; this effect can be used as a temperature sensor or as a voltage reference.
The current semiconductor diode voltage characteristics can be adjusted by selecting the semiconductor material and the doping impurities introduced into the material during manufacture. These techniques are used to create special purpose diodes that perform many different functions. For example, the diode is used to regulate the voltage (Zener diode), to protect the circuit from high voltage wave (avalanche diode), to set radio and TV receiver electronically (varactor diode), to produce radio frequency oscillation (tunnel diode, Gunn diode) IMPATT diodes), and to produce light (light-emitting diodes). Tunnel, Gunn and IMPATT diodes show negative resistance, which is useful in microwave and switching circuits.
Diodes, both vacuum and semiconductor, can be used as sound blowing generators.
Maps Diode
History
Thermionic diodes (vacuum tubes) and solid-state diodes (semiconductors) were developed separately, roughly at the same time, in the early 1900s, as radio-receiving detectors. Until the 1950s, vacuum diodes were more commonly used in radios because the starting points of contact-semiconductor diodes were less stable. In addition, most receiver devices have a vacuum tube for amplification that can easily have a thermionic diode included in a tube (eg a 12SQ7 double-decoded triode), and a gas rectifier rectifier and a gas rectifier capable of handling multiple high voltages./high current rectification task is better than semiconductor diodes (such as selenium rectifiers) available at that time.
Hollow tube diodes
In 1873, Frederick Guthrie observed that the white hot metal ball that was stretched so close to the electroscope would emit a positively charged electroscope, but not a negatively charged electric electroscope.
In 1880, Thomas Edison observed a direct current between the heat and non-heat elements in the bulb, which was then called the Edison effect, and was granted a patent on the application of phenomena for use in the dc voltmeter.
About 20 years later, John Ambrose Fleming (scientific advisor for Marconi Company and former Edison employee) realized that the Edison effect could be used as a radio detector. Fleming patented the first true thermionic diode, the Fleming valve, in England on November 16, 1904 (followed by U.S. Patent 803,684 in November 1905).
Throughout the era of vacuum tubes, valve diodes are used in almost all electronics such as radio, television, sound systems and instrumentation. They gradually lost market share starting in the late 1940s due to selenium rectifier technology and then to semiconductor diodes during the 1960s. Today they are still used in some high power applications where their ability to withstand transient voltages and their robustness gives them an advantage over semiconductor devices, and in musical instruments and audiophile applications.
Solid-state diode
In 1874, German scientist Karl Ferdinand Braun discovered "unilateral conduction" through contact between metals and minerals. Indian scientist Jagadish Chandra Bose was the first to use crystals to detect radio waves in 1894. The crystal detector was developed into a practical tool for wireless telegraphy by Greenleaf Whittier Pickard, who invented the silicon crystal detector in 1903 and received a patent for it on November 20, 1906 Other researchers tried various other minerals as detectors. The semiconductor principle is not known by the developer of this early rectifier. During the 1930s advanced physics understanding and in the mid-1930s researchers at Bell Telephone Laboratories recognized the potential of crystal detectors for applications in microwave technology. Researchers at Bell Labs, Western Electric, MIT, Purdue and in the United Kingdom intensively developed point-point dies ( crystal rectifiers or crystal diodes ) during World War II for applications in radar. After World War II, AT & amp; T uses this in their microwave towers that alternate the United States, and many sets of radar use it even in the 21st century. In 1946, Sylvania began offering 1N34 crystalline diodes. During the early 1950s, junction diodes were developed.
Etymology
At the time of their discovery, asymmetric conduction devices were known as rectifiers. In 1919, the year-old tetrodes were created, William Henry Eccles coined the term diode from the Greek root in , and ode (from ???? ), which means 'path'. The word diode , however, as well as triode, tetrode, pentode, hexode , has been used as a term from multiplex telegraph.
Rectifiers
Although all diodes are improved, the term rectifier is usually applied to diodes intended for power supply applications in order to distinguish them from diodes intended for small signal circuits.
Hollow tube diodes
The thermionic diode is a thermionic valve device composed of a sealed glass or metal envelope, containing two electrodes: a cathode and a plate. The cathode is not directly heated or directly heated . If indirect heating is used, the heater is included in the envelope.
In operation, the cathode is heated to red heat (800-1000 ° C). A heated cathode is directly made of tungsten wire and heated by a current passing it from an external voltage source. The cathode is heated indirectly heated by infrared radiation from the nearest heater formed from the Nichrome wire and supplied with the current provided by an external voltage source.
The operating temperature of the cathode causes it to release electrons to the vacuum, a process called thermionic emissions. The cathode is coated with oxides of alkaline earth metal, such as barium and strontium oxide. It has a low work function, which means that they are easier to emit electrons than uncoated cathodes.
The plates, not heated, do not emit electrons; but it can absorb it.
The alternating voltage to be fixed is applied between the cathode and the plate. When the plate voltage is positive to the cathode, the electrostatic plate draws the electrons from the cathode, so that the electron current flows through the tube from the cathode to the plate. When the plate voltage is negative with respect to the cathode, no electrons are emitted by the plates, so no current can pass from the plate to the cathode.
Semiconductor Diode
Contact-point diode
The diode contact point was developed from the 1930s, out of the early crystal detector technology, and is generally used in the 3 to 30 gigahertz range. The contact-point diode uses a small diameter metal wire that is in contact with the semiconductor crystal, and is a type of contact not welded or a welded contact type. The construction of non-weld contacts uses the Schottky barrier principle. The metal side is the pointy end of the small diameter wire that comes into contact with the semiconductor crystals. In the welded contact type, a small P region is formed on another N type crystal around the metal point during manufacture by simply passing a relatively large current through the device. The diode contact point generally shows lower capacitance, higher forward resistance and larger reverse leakage than the diode connection.
Junction diode
p-n diode connection
The p-n connection diodes are made of semiconductor crystals, usually silicon, but germanium and gallium arsenide are also used. Dirt is added to it to create a region on one side containing a negative charge carrier (electron), called an n-type semiconductor, and an area on the other side containing a positive hollow carrier (hole), called a p-type semiconductor. When the n-type and p-type materials are bonded together, a momentary electron stream occurs from side n to the p-side producing a third region between the two in which no load carriers are present. This area is called the depletion region because there is no carrier charge (either electrons or holes) in it. The diode terminal is attached to the n-type and p-type regions. The boundary between these two regions, called the p-n junction, is the place where the action of the diode takes place. When a high enough electrical potential is applied to the P side (anode) rather than to the N side (cathode), this allows the electrons to flow through the depletion region of the N-type to the P-type side. Intersections do not allow the flow of electrons in the opposite direction when the potential is applied in reverse, creating, in a sense, an electric valve.
Diode Schottky
Another type of junction diode, Schottky diode, is formed from a semiconductor-metal crossing rather than a p-n connection, which reduces the capacitance and increases the switching speed.
Current voltage characteristic
The behavior of a semiconductor diode in a circuit is given by the voltage-current characteristics, or the I-V graph (see graph below). The shape of the curve is determined by the transport of the carriers through the so-called depletion layer or depletion region at the p-n junction between different semiconductors. When a p-n junction is first made, the electron-band (cellular) conduction of the N-doped region spreads to the P-doped region where there is a large population of holes (a vacant place for electrons) by which the electrons "recombine". When an electron moves to rejoin the hole, the hole and electrons disappear, leaving a dopant-laden donor on the N side and a negative dopant at the P side. The area around the pn junction becomes exhausted by the operator and thus behaves as an insulator.
However, the width of the depletion region (called wide depletion) can not grow indefinitely. For each recombination of the created electron-hole pair, positive dopant ions are left in the N-doped region, and negatively charged dopant ions are made in the P-doped region. When recombination results and more ions are created, an increased electric field develops through a depletion zone that acts to slow down and eventually stop recombination. At this point, there is a potential "built-in" across the depletion zone.
Reversed bias
If an external voltage is placed across the diode with the same polarity as the installed potential, the depletion zone continues to act as an insulator, preventing significant flow of electrical current (unless electron-hole pairs are actively being made at the intersection by, for example, light, see photodiode). This is called the phenomenon of reverse bias .
Forward bias
However, if the polarity of the external voltage opposes the installed potential, recombination can once again run, generating substantial electrical current through a p-n connection (ie a large number of electrons and holes recombine at the junction). For silicon diodes, the installed potential is approximately 0.7 V (0.3 V for germanium and 0.2 V for Schottky). Thus, if an external voltage greater than and contrary to the applied voltage is applied, the current will flow and the diode is said to be "turned on" as it has been given forward bias . The diode is generally said to have a "threshold" voltage forward, on top of it conducting and under conduction that stops. However, this is only an approximation because of the fine front characteristics (see graph I-V above).
The I-V diode character can be approximated by four operating areas:
- In very large reverse bias, outside the inverse peak voltage or PIV, a process called inverse damage occurs that causes a large current increase (eg, large numbers of electrons and holes are created, and away from the pn junction) which usually damage the device permanently. The avalanche diode is deliberately designed to be used that way. In the Zener diode, the PIV concept does not apply. The Zener diode contains highly-pinced pn junctions which allow the electrons to tunnel from the valence band from the p-type material to the conduction band of the n-type material, so that the return voltage is "clamped" to a known value (called Zener voltage ), and an avalanche does not occur. Both devices, however, do have limits for the maximum current and power they can withstand in the clipped voltage region. Also, following the end of forward conduction in each diode, there is a backflow for a short time. The device does not achieve full blocking capability until the backflow stops.
- For a bias less than PIV, the backflow is very small. For a normal P-N rectifier diode, the return current through the device in the micro-ampere (ÂμA) range is very low. However, this depends on the temperature, and at sufficiently high temperatures, a large amount of reverse current can be observed (mA or more). There is also a small surface leakage current caused by electrons just going around the diode as if it were an imperfect insulator.
- With a small forward bias, where only small forward currents are performed, the exponential voltage current curve corresponds to the ideal diode equation. There is a definite forward voltage at which the diodes start performing significantly. This is called the knee voltage or the cut-in voltage and is equal to the barrier potential of the p-n connection. This is a feature of the exponential curve, and appears sharper on a scale now more compressed than in the diagram shown here.
- In the larger forward current the voltage current curve begins to be dominated by the ohmic resistance of the bulk semiconductor. The curve is no longer exponential, it is asymptotic to a straight line whose slope is mass resistance. This region is very important for power diodes. Diodes can be modeled as ideal diodes in series with fixed resistors.
In a small silicon diode that operates on the identifier current, the voltage drop is about 0.6 to 0.7 volts. Different values ​​for other diode types - Schottky diodes can be rated as low as 0.2 V, germanium diodes 0.25 to 0.3 V, and red or blue light transmitters (LEDs) can have a value of 1.4 V and 4 respectively , 0 V.
At higher currents, the diode's forward voltage drop increases. A drop of 1 V to 1.5 V is typical of a full measured current for power diodes.
Shockley diode equations
The Shockley diode equation ideal or legal diode (named after the bipolar co-inventor William Bradford Shockley) provides the IV characteristics of the ideal diode either forward or backward bias (or no bias ). The following equation is called the ideal diode equation Shockley when n , the ideal factor, set equal to 1:
Where
- I is a diode current,
- I S is the reverse bias saturation current (or current scale),
- V D is the diode voltage,
- V T is the thermal stress, and
Tegangan termal V T kira-kira 25,85 mV pada 300 K, suhu yang mendekati "suhu ruangan" yang umumnya digunakan dalam perangkat lunak simulasi perangkat. Pada suhu berapa pun, ini adalah konstanta yang dikenal dengan:
where k is the Boltzmann constant, T is the absolute temperature of the pn junction, and q is the magnitude of the electron charge (the basic charge).
The inverted saturation current, I S , is not constant for the given device, but varies with temperature; usually more significantly than V T , so V D usually decreases as T .
The ideal diode equation Shockley or diode law is obtained assuming that the only current generating process in the diode is drift (due to electric field), diffusion, and generation of thermal recombination (RG ) (this equation is derived by setting n = 1 above). It also assumes that the R-G current in the depletion region is not significant. This means that the ideal Shockley ideal diode equation does not take into account the processes involved in the reverse damage and the photon assisted R-G. In addition, it does not describe the "level rise" of the I-V curve in high-forward bias due to internal resistance. Introducing the ideal factor, n, contributing recombination and carrier generation.
Under reverse bias , the exponential voltage in the diode equation is negligible, and the current is the constant (negative) reverse current value of - I S . The reverse breakdown region is not modeled by the Shockley diode equation.
Even for small forward biases, the exponential voltage is very large, since the thermal voltage is very small when compared. Reduced '1' in the diode equation is then ignored and the forward diode current can be approached by
The use of diode equations in circuit problems is illustrated in an article on diode modeling.
Small signal behavior
Pada tegangan maju kurang dari tegangan saturasi, kurva karakteristik tegangan versus arus dari kebanyakan dioda bukan garis lurus. Arus dapat didekati dengan sebagaimana disebutkan di bagian sebelumnya.
In detector and mixer applications, current can be estimated by the Taylor series. These strange terms can be omitted because they produce frequency components that are outside the tape pass from the mixer or detector. Even terms outside of the second derivative usually do not need to be included because they are small compared to second order terms. The desired current component is approximately proportional to the square of input voltage, so the response is called squared law in this region.
Reverse-recovery effect
After the end of the forward conduction in the p-n type diode, the reverse current can flow for a short time. The device does not reach its blocking capability until mobile content at the intersection runs out.
The effect can be significant when switching large currents very quickly. A number of "reversed recovery times" t r (in the order of tens of nanoseconds up to several microseconds) may be needed to remove the cost of recovering Q r from the diode. During this recovery time, the diodes can actually perform in the reverse direction. This can cause a large constant current in the reverse direction for a short time while the diode is reversed biased. The amount of backflow is determined by the operation circuit (ie, series resistance) and the diode is said to be in the storage phase. In the case of a particular real world, it is important to consider the harm caused by the effects of this non-ideal diode. However, when the rate of change of current is not so severe (eg channel frequency), the effect can be safely ignored. For most applications, the effect can also be ignored for Schottky diodes.
The return current stops abruptly when the stored charge is exhausted; This sudden stop is exploited in the diode recovery steps to produce very short pulses.
Type of semiconductor diode
Other uses for semiconductor diodes include temperature sensing, and calculating analog logarithms (see Applications of operational amplifier # Logarithm output).
Graphic symbol
The symbol used to represent a particular type of diode in a circuit diagram conveys a general electrical function to the reader. There are alternate symbols for some types of diodes, although the difference is small. The triangle in the symbol points toward the front, ie toward the conventional current flow.
Numbering and coding schemes
There are a number of common, standard and factory-made coding and coding schemes for diodes; the two most common are the EIA/JEDEC standards and the European Pro Electron standard:
EIA/JEDEC
The standard 1N-series numbering system EIA370 was introduced in the US by the EIO/JEDEC (Joint Electron Device Engineering Council) circa 1960. Most diodes have a 1-prefix designation (eg, 1N4003). Among the most popular in this series are: 1N34A/1N270 (germanium signal), 1N914/1N4148 (silicon signal), 1N400x (1A silicon power rectifier), and 1N580x (silicon 3A power rectifier).
JIS
The JIS semiconductor designation system has all the marking of a semiconductor diode beginning with "1S".
Pro Electron
The European Pro Electron coding system for active components was introduced in 1966 and consists of two letters followed by part codes. 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 diode, A = low power/signal, B = variable capacitance, X = multiplier, Y = rectifier and Z = voltage reference); as an example:
- AA-series germanium low-power/signal diode (e.g., AA119)
- BA-series low power silicon diodes/signals (eg, silicon RF BAT18 diode switching)
- Series-BY silicon rectifier series (eg, BY127 1250V, 1A diode rectifier) ​​
- BZ-series silicon Zener diodes (eg, BZY88C4V7 4.7V Zener diode)
Other common numbering systems (typically driven by the manufacturer) include:
- Germanium GD series diodes (eg, GD9) - this is a very long coding system
- OA-series germanium diodes (eg, OA47) Ã, - sequence encodings developed by Mullard, a British company
As well as this general code, many manufacturers or organizations have their own systems - for example:
- HP diode 1901-0044 = JEDEC 1N4148
- British military diode CV448 = Mullard Type OA81 = GEC type GEX23
Related devices
- Rectifier
- Transistor
- Thyristor or silicon-controlled rectifier (SCR)
- TRIAC
- DIAC
- Varistor
In optics, the device is equivalent to a diode but with a laser beam will be an Optical Insulator, also known as Optical Diode, which allows light to pass only in one direction. It uses the Faraday Rotator as the main component.
Apps
Radio demodulation
The first use for diodes is the demodulation of radio broadcast amplitude modulation (AM). The history of this discovery is deeply treated in radio articles. In summary, the AM signal consists of alternating positive and negative peaks of radio carrier waves, whose amplitude or envelope is proportional to the original audio signal. The diode rectifies the AM radio frequency signal, leaving only the positive peak of the carrier wave. Audio is then extracted from an improved carrier wave using a simple filter and fed to an audio amplifier or transducer, which generates sound waves.
In microwaves and millimeter wave technology, beginning in the 1930s, researchers improved and shrunk crystal detectors. The point contact diode ( crystal diode ) and the Schottky diode are used in radar, microwave and millimeter wave detectors.
Power conversion
Rectifiers are built from diodes, where they are used to convert alternating current (AC) into direct current (dc). The automotive alternator is a common example, where diodes, which fix the AC to dc, provide better performance than the commutator or earlier, dynamo. Similarly, the diode is also used in Cockcroft-Walton voltage multipliers to convert AC to higher ac voltage.
Over voltage protection
Diodes are often used to perform high voltage breakage from sensitive electronic devices. They are usually reversed-biased (non-cultivated) under normal circumstances. When the voltage rises above the normal range, the diode becomes forward biased (perform). For example, diodes are used in (motor and H-bridge driving motors) and relay circuits to shut down coils quickly without damaging the expected voltage spikes. (The diode used in this kind of application is called a flyback diode). Many integrated circuits also incorporate diodes on connection pins to prevent external voltages damaging their sensitive transistors. Special diode is used to protect from overload voltage at higher power (see Diode type above).
Logic gates
Diodes can be combined with other components to build AND AND OR logic gates. This is referred to as logic diode.
Ionizing radiation detector
In addition to the light, mentioned above, semiconductor diodes are sensitive to more energetic radiation. In electronics, cosmic rays and other sources of ionizing radiation cause noise pulses and single and double bit errors. This effect is sometimes exploited by a particle detector to detect radiation. A particle of radiation, with thousands or millions of volts of energy electrons, produces many charge carriers, because its energy is stored in semiconductor materials. If the depletion layer is large enough to capture the entire shower or to stop heavy particles, a fairly accurate measurement of particle energy can be made, simply by measuring the charge performed and without the magnetic spectrometer's complexity, etc. This semiconductor radiation detector requires efficient and uniform collection of charges and a low leakage current. They are often cooled by liquid nitrogen. For longer particles (about a centimeter), they require a very large depletion depth and large area. For close-range particles, they require contacts or semiconductors that are not exhausted on at least one surface to be very thin. The return voltage is biased near the damage (about one thousand volts per centimeter). Germanium and silicon are common materials. Some of these detectors sense position and energy. They have a limited life, especially when it detects heavy particles, because of radiation damage. Silicon and germanium differ greatly in their ability to convert gamma rays into electron rain.
Semiconductor detectors for high-energy particles are used in large quantities. Due to fluctuations in energy loss, accurate measurements of stored energy are less useful.
Temperature measurement
The diode can be used as a temperature gauge, since the forward voltage drop across the diode depends on the temperature, as in the temperature sensor of the silicon bandgap. From the Shockley ideal diode equations given above, it may appear that the voltage has a positive temperature coefficient (in constant current), but usually the variation of the reversed saturation current of the term is more significant than the variation in terms of thermal stress. Therefore, most diodes have a negative temperature coefficient , usually -2 mV/? C for silicon diodes. The temperature coefficient is approximately constant for temperatures above about 20 kelvins. Some graphs are given for the 1N400x series, and CY7 cryogenic temperature sensors.
Referrer
The diode will prevent the current in an undesirable direction. To supply electricity to the electrical circuit when power failure, the circuit can draw current from the battery. An uninterruptible power supply can use a diode in this way to ensure that the current is only taken from the battery when needed. Likewise, small boats typically have two circuits each with their own batteries/batteries: one used for starting engines; one is used for household. Typically, both are filled from a single alternator, and heavy-duty charge-charge diodes are used to prevent higher-cost batteries (usually engine batteries) from battery usage at lower costs when the alternator is not running.
Diodes are also used in electronic music keyboards. To reduce the number of cables required in electronic music keyboards, these instruments often use keyboard matrix circuits. The keyboard controller scans rows and columns to determine which records the player has pressed. The problem with matrix circuits is that, when multiple records are pressed at once, the current can flow backwards through the circuit and trigger the "phantom button" which causes the "ghost" to record to play. To avoid triggering unwanted records, most keyboard matrix circuits have diodes that are soldered with buttons under each keyboard music key. The same principle is also used for switch matrices in solid-state pinball machines.
Clipper Waveform
Diodes can be used to limit the positive or negative travel of the signal to the specified voltage.
Clamper
Diode clamp circuits can pick up periodic alternating current signals that oscillate between positive and negative values, and vertically replace them so that either positive, or negative peaks occur at a given level. Clamper does not limit the exclusion of peak-to-peak signals, moving all signals up or down so as to place a peak at the reference level.
Abbreviation
The diode is usually referred to as D for the diode on the PCB. Sometimes the abbreviation CR for crystal rectifier is used.
See also
- Active rectification
- Diode Modeling
- Junction diode
- Lambda diode
- p-n junction
- Small signal model
References
External links
- Diodes and Rectifiers - Chapter on All About Circuits
- Functional Structure and Behavior of Diode PIN - PowerGuru
- Interactive and animation
- Interactive Diodes Semiconductor Diode, Cambridge University
- Animation Tutorial Flash Diode Schottky
- Datasheets/Databooks
- Discrete Databook (Historical 1978), National Semiconductor (now Texas Instruments)
- Discrete Databook (Historical 1982), SGS (now STMicroelectronics)
- Discrete Databook (Historical 1985), Fairchild
Source of the article : Wikipedia
0 Comments