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Introduction Characteristics of Reverse Forward Reverse Breakdown role of the working principle type detection method to construct classification point-contact surface contact type key type alloy type diffusion mesa type epitaxial planar type alloy diffusion type Shaw Schottky use classification feature category conductivity Forward Characteristics Reverse Characteristics Parameter Symbol Recognition luminous main classification nomenclature relationship test quality bidirectional trigger voltage detection detection detection of infrared light-emitting luminescence detection of infrared detection of other photosensitive photosensitive detection Detection of laser detection varactor dual base detection (eleven) bridge pile testing (twelve) high voltage silicon stack testing (thirteen) variable resistance testing (fourteen) Schottky reverse feature detection test section Edit this paragraph parameter expansion Introduction diodes (English: Diode), electronic components among device having two electrodes, allowing only a single direction of current flow. The use of many of the functions is the application of its rectification. The varactor diode (Varicap Diode) is used as the electronic adjustable capacitor diodes have the most current direction we usually call "rectifier (Rectifying)" function. The most common feature is the diode allows current from a single direction only through (called the forward bias), the reverse is blocked (called reverse bias). Thus, the diode can be thought of as an electronic version of a check valve. However, in practice the diode does not exhibit such a perfect directivity and off, but the more complex non-linear electrical characteristics - This is a particular type of diode technology decision. Diode is used in addition to the outside with a way to make the switch, there are many other features including Diode early "whisker crystals (" Cat's Whisker "Crystals)" as well as vacuum tubes (English called "hot free valve (Thermionic Valves)") . Most of today's most common is the use of a diode semiconductor material such as silicon or germanium. Edit this paragraph sexual characteristics Forwarddiode icon
plus the forward voltage, the initial part of the forward characteristics, the forward voltage is very small, not enough to overcome the PN junction blocking effect of the electric field, the forward current is almost zero, this period is called dead zone. This does not make the forward voltage diode voltage called dead zone. When the forward voltage is greater than the voltage after the dead zone, PN junction electric field to be overcome, the diode is forward current versus voltage increases rapidly. In normal use the current range, the diode conduction terminal voltage is almost unchanged, this voltage is called the diode forward voltage. When the forward voltage across the diode exceeds a certain value, the electric field is weakened quickly, the current rapid growth of the diode forward. Is called the threshold voltage or the threshold voltage, the silicon tube of about 0.5V, germanium tube of about 0.1V. Silicon diode's forward voltage drop of about 0.6 ~ 0.8V, germanium diode's forward voltage drop of about 0.2 ~ 0.3V. Reverse of applied reverse voltage does not exceed a certain range, current through the diode is the minority carrier drift movement formed by reverse current. Due to the reverse current is very small, the diode is off. This reverse current is also called the reverse saturation current or leakage current, the diode reverse saturation current greatly affected by temperature. General silicon tube reverse current is much smaller than the germanium tube, low-power silicon tube saturation current in nA response magnitude, low-power germanium tube μA magnitude. Temperature, the semiconductor thermal emission, increase in the number of minority carriers, the reverse saturation current is increased. Breakdown applied reverse voltage exceeds a certain value, the reverse current suddenly increases, a phenomenon known as electric breakdown. Cause electrical breakdown threshold voltage is called diode reverse breakdown voltage. Electrical breakdown diode lose unidirectional conductivity. If the diode is not caused by overheating due to electrical breakdown, then the one-way conductivity will be permanently destroyed, after the removal of the applied voltage, its performance can still be restored, otherwise it will damage the diode. Thus should avoid the use of diode reverse voltage applied is too high. A unidirectional conducting diode is a two-terminal device, an electronic and crystal diodes of the diode, the diode electron heat loss because of the filament, lower efficiency than the crystal diode, so now rarely seen, much more common, and common is the crystal diode. Unidirectional diode electrical properties, in almost all electronic circuits, to be used in a semiconductor diode, which in many circuit plays an important role, it is the birth of the first semiconductor device, which is also widely used. Diode voltage drop: silicon diodes (non-luminous type) forward voltage drop 0.7V, germanium tube forward voltage drop of 0.3V, LED forward voltage drop will vary with different light color and different. There are three colors, the specific reference values drop as follows: Red light emitting diode drop of 2.0 - 2.2V, the yellow light-emitting diode voltage drop of 1.8-2.0V, the green light-emitting diode drop of 3.0-3.2V, the normal glow when the rated current is about 20mA. Diode voltage and current is not a linear relationship, so the diode in parallel with a different time to adapt to the resistance connected. Characteristic curve with the same PN junction diode with unidirectional conductivity. Typical silicon diode volt-ampere characteristic curve (Figure). Plus a forward voltage of the diode, when the voltage value is small, a very small current; when the voltage exceeds 0.6V, the current begins to increase exponentially, usually called the turn-on voltage of the diode; when the voltage reaches about 0.7V, diodes are fully ON state, the voltage is usually called the diode turn-on voltage, expressed by the symbol UD. For the germanium diode turn-on voltage of 0.2V, UD breakover voltage is approximately 0.3V.plus a reverse voltage of the diode, when the voltage value is small, the current is very small, the current value of the reverse saturation current IS. When the reverse voltage exceeds a certain value, the current begins to increase sharply, called reverse breakdown voltage of the diode call this reverse breakdown voltage, expressed by the symbol UBR. Different models UBR diode breakdown voltage values vary greatly, from tens of volts to several thousand volts. Reverse Breakdown zener reverse breakdown by Zener breakdown mechanism is divided into two cases and avalanche breakdown. In the case of high doping concentration, because the barrier zone width is small, the reverse voltage is larger, the destruction of the barrier region covalent bond structure, the valence electrons from the covalent binding, resulting in electron - hole pairs , resulting in a sharp increase in current, which is called zener breakdown. If the doping concentration is low, the potential barrier region wide width, not prone to the Zener breakdown. Another avalanche breakdown avalanche breakdown. When the reverse voltage is increased to a large value, the applied electric field to accelerate the electron drift velocity, and thus the covalent bond valence electrons collide dislodging the valence electron covalent bond, generating new electron - hole pairs. The newly generated electron - hole and then accelerated by an electric field to dislodge remaining valence electrons avalanche carriers increases, resulting in a sharp increase in current, which is called avalanche breakdown. Whatever the breakdown, if its current unchecked, could cause permanent damage to the PN junction. Edit this paragraph is the most common effect of the diode is one of electronic components, it is the biggest feature is the way conductive, that is, the current can only flow in one direction through the diode, the diode rectifier circuit role of, the detector circuit, voltage regulator circuit, various modulation circuits are mainly constituted by a diode, the principle is very simple, because of diodes and other components of the invention, we now have a variety of electronic information the birth of the world, since the role of the diode so much so that we This component should be how to detect it, is actually very simple just use the multimeter to measure the resistance profile look forward resistance if very small, which indicates a large inverted resistivity if this diode is good. For such basic elements that we should firmly grasp his role as well as the basic principles of circuit, so as to learn for the future of electronic technology to lay a good foundation. [1] Edit this section works Diode
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crystal diode is a p-type semiconductor and n-type semiconductor forming a pn junction is formed at the interface space charge layer at the sides, and has a self field. When there is no applied voltage, since the pn junction on both sides of the carrier concentration and diffusion current caused by the difference of the drift electric field causes self currents equal in electrical balance. When the outside has a positive bias voltage, the external electric field and the mutual self-built electric consumption suppression role of the carrier diffusion current caused by an increase of the forward current. When the outside world when the reverse bias voltage, the external electric field and the electric field to further strengthen self-built, forming a certain reverse voltage range and reverse bias voltage value independent of the reverse saturation current I0. When the applied reverse voltage is high to a certain extent, pn junction space charge layer in the electric field strength reaches a critical value generating process of the multiplication of carriers, a large amount of electron-hole pairs, resulting in a large value of the reverse breakdown current , called the diode breakdown. pn junction reverse breakdown Zener breakdown and avalanche breakdown of the points. Edit this section Type Diode There are many types, according to the semiconductor material used can be divided into germanium diode (Ge tube) and a silicon diode (Si tube). According to its different uses, can be divided into detector diodes, rectifier diodes, zener diodes, switching diodes, isolation diodes, Schottky diodes, light emitting diodes, silicon power switching diodes, rotating diodes. In accordance with the pipe core structure can be divided into point contact diode, surface contact type diodes and planar diodes. Point contact diode with a very thin metal wire pressed against the smooth surface of a semiconductor wafer, through a pulse current, the contact wire at one end of the wafer firmly sintered together, forming a "PN junction." As the point contact, allowing only a small current (less than tens of milliamps), suitable for high frequency small current circuits, such as radio detection. Surface contact type diode "PN junction" larger, allows a large current (several amps to tens of A), mainly for converting the alternating current into direct current of the "rectification" circuit. Planar diode is a special silicon diode, it is not only through the larger current, and the performance is stable and reliable, and more for the switch, pulse and high frequency circuits.SMD diode
Edit this paragraph detection method to detect small power crystal diode A. discriminate between positive and negative electrodes (a) observation symbol marks on the shell. The housing of the diode is usually a diode symbol marked with triangular arrowhead is positive, the other side is a negative electrode. (B) observe the colored dots on the shell. Case in point-contact diode, usually marked with a polarity dots (white or red). General standard colored end point is positive. There diode superscript colored ring with colored ring at one end was negative. (C) the resistance of the smaller one measurement prevail, black table document end is positive, the red table document end was negative.with a silver band end is negative
(d) observation diode housing with silver band end is negative. B. Detection maximum reverse breakdown voltage. For alternating current, because the constantly changing, so is the maximum reverse voltage diode withstand peak AC voltage. Bidirectional trigger diode detector placed in the multimeter DC voltage corresponding block. Provided by the megger test voltage. Test, shaking megger, Wan same method to measure VBR values. Finally, the VBO and VBR comparing the absolute value of the difference between the two is smaller, the symmetry of the measured two-way trigger diode as possible. Transient voltage suppression (TVS) diode test tube A. Use a multimeter to measure the quality of the single-pole type to TVS, in accordance with the ordinary diode measurement method can measure its positive and negative resistance, generally positive resistance 4kΩ about reverse resistance is infinite. For bi-polar type TVS, any exchange of red, black pen to measure the resistance between the two pins should be infinite, otherwise, indicating poor performance or damaged pipes. High-frequency variable resistance diode detection and identification of positive and negative frequency variable resistance diode with ordinary diode is the difference in appearance of different colors of its color,R4i Gold 3DS, ordinary diodes mark color is black, while the high frequency diode color variable resistance color was light. Law and ordinary diode polarity similar to that end with the green ring is negative, not positive at one end with a green ring. Varactor detection will multimeter red, black pen swap how measurement varactor resistance between the two pins should be infinite. If the measurement, it was found a slight wobble meter pointer to the right or the resistance is zero, indicating a leakage test varactor failure or breakdown has been broken. Detection of monochromatic light-emitting diodes attached an external multimeter saving 1.5V batteries, place the multimeter R × 10 or R × 100 block. This access method is equivalent to giving a multimeter in series on a 1.5V voltage, so that the detection voltage increased to 3V (light-emitting diode turn-on voltage of 2V). Detection, two tables with a multimeter pen rotation of two light-emitting diodes in contact pin. If the tube performance is good, there must be a normal light, this time, the black table document for the positive red table document for the cathode. A. Detection of infrared light emitting diode infrared emitting diode discriminant positive and negative electrodes. Infrared light emitting diode has two pins, usually longer pin is positive, the short pin is negative. Because infrared light emitting diode are transparent, so that the envelope of the electrode is clearly visible, the larger a wide internal electrode as the anode, and a narrow and small is positive. B. the first measurement of the red light-emitting diode, the reverse resistance, usually forward resistance should be 30k or so, reverse resistance to 500k or more, so the tubes can be used normally. Infrared receiver diode pin polarity detection A. Identification (a) identification from the appearance. Common infrared receiver diode exterior color was black. Identification pin, face light window, from left to right, respectively, positive and negative. Also in infrared receiver diode tube top with a small miter plane, usually with a pin at one end of this oblique plane is negative, the other side is positive. (B) determine the ordinary diode with a multimeter first positive and negative electrodes of the methods are reviewed, namely exchange red, black pen tube measured twice the resistance between the two pins, the normal, the resultant resistance should be one large and one small. For one time with a lower value, the red lead connection pipe footsteps as the anode, black table document pin is positive. B. detection performance is good or bad. Power block with a multimeter measuring infrared receiver diode forward and reverse resistance, according to the positive and negative resistance value of the size, you can determine the initial infrared receiver diode is good or bad. A. Detection of laser diode ordinary diode according detect positive and negative resistance method, the laser diode can be determined by the order of the pin arrangement. But testing should note that due to the laser diode's forward voltage drop of the diode to be larger than normal, so the detection of positive resistance, the meter pointer slightly to the right of public deflect it. [2] Edit this paragraph classification structure semiconductor PN junction diode which relies mainly on the work. PN junction integral with point-contact and Schottky type diode is also included within the scope of the general. Both models include the account, according to PN-made surface structure characteristics of the crystal diode classified as follows: Point-contact point contact diode germanium or silicon material in a single-chip pressure touch a metal needle, and then through the current France formed. Thus, the PN junction capacitance is small, suitable for high frequency circuits. However, compared with the surface junction, point contact diode forward characteristics and reverse characteristics are poor, therefore, can not be used in high current and rectification. Because the structure is simple, so the price is cheap. Surface contact type surface area of contact type or called the PN junction diode is made of alloy method or the diffusion method, and because of this large area PN junction diode, can withstand high current, but also large electrode capacitance. Such devices are suitable for rectification, and is not suitable for high frequency circuits. Key-type key-type germanium or silicon diodes in a single chip molten gold or silver filaments formed. Its characteristics between the point-contact diode and diode between alloy type. Compared with the point contact type, while the PN junction diode bond capacity slightly increased, but the forward characteristic is particularly excellent. Make more switching is sometimes also applied to detection and power rectifier (less than 50mA). In the key-type diodes, welding diodes sometimes called gold gold bond type, welding diode is sometimes called silver silver key type. Alloy type the N-type silicon, germanium or a single chip, by adding indium alloy, method of production of aluminum and other metals and the formation of a PN junction. Forward voltage drop is small, suitable for high current rectification. PN junction reverse when its electrostatic capacity, it is not suitable for high-frequency detector and high frequency rectification. Diffusion of the P-type impurity at a high temperature gas, heating N-type germanium or silicon-chip, the single wafer surface becomes a P-type, this method PN junction. PN junction forward voltage drop due to the small, suitable for high current rectification. Recently, the use of high current rectifiers mainstream has been transferred to the silicon-silicon alloy-type diffusion. PN junction mesa-type method, although the production and diffusion of the same type, however, retaining only its essential part of the PN junction, the unnecessary portion of the etched using drugs. Its remaining part will be presented mesa-shaped, hence the name. Initial production of the mesa, the semiconductor material is made using the diffusion method. So, again this mesa called diffusion mesa type. For this type, it seems high current rectifier product model is small, and low current switching has a lot of product models. Planar semiconductor chip (mainly N-type silicon film), the P-type impurity diffusion using the silicon oxide film on the surface of the shielding effect of the N-type silicon chip spread only part of the selective formation of the PN knot. Therefore, no need to adjust the PN junction area of drugs corrosion. Because the semiconductor surface is too smooth production, hence the name. And, PN bound surface, because the oxide film, so that the stability and the public long life type. Initially, the semiconductor material used is formed by using an epitaxial method, it is again referred to as planar epitaxial planar type. On the planar diode,3DS Linker, seem to use for high current rectifier model is small, and for small current switch models are used a lot. Alloy diffusion type which is an alloy type. Alloy material is a material easy to spread. The material produced by the hard skillfully blending impurities, can be spread over together with the alloy so as to form a PN junction has been obtained in an appropriate impurity concentration distribution. This method is suitable for the manufacture of high sensitivity varactors. Epitaxial epitaxial surface long process manufacturing PN junction diode formed. Manufacturing requires very skilled. Because it can freely control the distribution of different concentrations of impurities, it is suitable for manufacturing high-sensitivity varactor diodes. Schottky basic principle is: the metal (such as lead) and semiconductor (N-type silicon) on the contact surface, with the formation of Schottky to block reverse voltage. Schottky rectifier with PN junction there is a fundamental difference between action principle. Its voltage level is only about 40V. Its specialty is: very fast switching speed: Reverse Recovery Time trr particularly short. Therefore, to make switching diodes and low voltage high current rectifier diode. Edit this section use classification detector diode detector diode's main role is the high-frequency signal frequency signal detected. Their point-contact structure, so its junction capacitance is small, the operating frequency is higher. Generally used germanium material. The principle, the input signal from the modulation signal detector taken to the size of the rectified current (100mA) as the boundary of the output current is less than 100mA generally called detection. Germanium point contact type, operating frequency up to 400MHz, the forward voltage drop is small, junction capacitance, detector efficiency, frequency characteristics, good for 2AP type. Similar to the point-contact diode used as the detector, except for the detection, but also can be used for clipping, clipping, modulation, mixers, switches and other circuitry. FM detector is also promising a good two special characteristics of diode assembly consistency. 2. Rectifier diode on the principle concerned, obtained from the input AC is rectified DC output. To the size of rectified current (100mA) as the boundary of the output current greater than 100mA usually called rectification. Surface junction in the junction capacitance is large, typically 3kHZ less. Maximum reverse voltage from 25 volts to 3000 volts of A ~ X of 22 files. Classified as follows: ① 2CZ type silicon semiconductor rectifier diode, ② QL-type silicon bridge rectifier, ③ high voltage silicon stack for TV 100KHz frequency near the 2CLG type.internal structure
3. limiter diode diode forward, its forward voltage drop essentially unchanged (silicon tube is 0.7V, germanium tube 0.3V). With this feature, the circuit element used as a limiter, the signal amplitude can be limited to a certain range. Most of the diode can be used as a limiter. There are elephant conservation and high-frequency instrument with such a dedicated zener diode limiter. To make these diodes have a particularly strong effect of limiting the amplitude of the sharp, usually with silicon diodes. Such components are also for sale: According to limit the voltage required, the number of necessary rectifier diodes in series to form a whole. 4 refers to the modulation diode is typically a diode ring modulator exclusive. Consistency is a good four diode forward characteristic of the assembly. Even though there are other varactor modulation purposes, but they are usually used directly as FM. 5 mixer diodes mode using a diode mixer, 500 ~ 10,000 Hz in frequency range, the use of Schottky diodes and a point contact type. 6 Zoom diode diode amplification, generally have to rely on tunneling diodes and diode body effect as the amplification of negative resistance devices, as well as with varactor parametric amplification. Therefore, the amplification is typically a diode tunnel diode, body effect and varactor diode. 7. Switching Diode Forward Voltage role in the resistance is small, in the conduction state, the equivalent of a switch is turned on; the reverse voltage is applied, the resistance is large, in the off state, like a broken switch. The use of diode switching characteristics, can be composed of a variety of logic circuits. There are a small current (10mA level) of the logic operations and the use of hundreds of milliamperes core excitation switching diodes. Low current switching diodes are usually a little touch-type and bond type, etc. diodes, also work at high temperatures may also silicon diffusion, mesa and planar diodes. Switching diode specialty is fast switching speed. The Schottky diode special short switching time, and thus is ideal for switching diodes. 2AK type point contact for the medium-speed switching circuits; 2CK planar contacts for high-speed switching circuit; for switches, limiters, such as clamping or detector circuit; Schottky (SBD) silicon high current switch, forward voltage drop Small, fast and efficient. 8 varactor for automatic frequency control (AFC) and the tuning said with a small power diode varactor. Japanese firms also have many other popular name. By applying a reverse voltage; PN junction capacitance to change. Therefore, the automatic frequency control is used, the scanning oscillator, frequency modulation and tuning purposes. Usually, though the diffusion of silicon diode, but also can be diffused alloy, epitaxial-binding, such as double diffusion special production of diodes, these diodes as the voltage, the rate of change of the electrostatic capacity which is particularly great. Junction capacitance changes with reverse voltage VR, instead of the variable capacitance tuning circuit for the oscillator circuit, phase locked loop used in the TV tuner and the tuning of channel conversion circuit, and more to the silicon material. 9 a diode frequency multiplier multiplying the frequency of the diode effect, there are relying varactor frequency multiplier and rely on a step (i.e. CML) diode frequency multiplier. Frequency multiplier with varactor known varactors, varactor and automatic frequency control while varactor work the same, but the structure of the reactor was able to withstand high power. Step diode is also known as step recovery diodes, switching from on to off when the reverse recovery time trr short, and therefore its specialty is closing rapidly transfer time becomes significantly shorter. If the step sine wave applied to the diode, then, because tt (transfer time) is short, so the output waveform abrupt be pinched off, it can produce a lot of high frequency harmonics. 10 is the use of such tubes Zener diode reverse breakdown characteristics of the diode formed in the circuit the voltage across it remains substantially constant, stabilize the voltage. Is to replace the diode voltage regulator electronic products. Was produced as silicon diffusion or alloy type. Is the reverse breakdown characteristic curve abrupt change of the diode. Standard voltage as the control voltage and the production of use. The terminal voltage diode operation (also known as Zener voltage) from about 3V to 150V, at intervals of 10%, which could be divided into several levels. In terms of power, but also from 200mW to 100W or more products. Working in reverse breakdown state, silicon materials, dynamic resistance RZ is very small, usually 2CW, 2CW56 etc.; diode reverse the two complementary series to reduce the temperature coefficient is 2DW type. Zener diode temperature coefficient α: α is the temperature changes every 1 ℃ regulation value variation. Stable voltage is less than 4V tube has a negative temperature coefficient (belonging Zener breakdown), which elevated temperatures stabilize voltage drop (the valence electron temperature rise higher energy); stable voltage greater than 7V tube having a positive temperature coefficient (belonging avalanche breakdown), the temperature rise when the regulated voltage value (amplitude of the temperature increase of the atom, impeding movement of carriers); and stable voltage between 4 ~ 7V tube, the temperature coefficient is very small, nearly zero (zener breakdown and avalanche breakdown both). 11.PIN diode (PIN Diode) is in the P and N regions sandwiched between a layer of intrinsic semiconductor (or low-concentration impurity semiconductor) structure of crystal diode. In PIN I was "intrinsic" meaning in English abbreviation. When the operating frequency of more than 100MHz, the minority carriers as the memory effect and the "intrinsic" layer, the transit time effect, the diode rectifying action and become lost impedance components, and the impedance value with partial set the voltage change. At zero bias or DC reverse bias, the "intrinsic" area high impedance; in the DC forward bias, due to carrier injection "intrinsic" area, leaving the " sign "area presents a low impedance state. Therefore, the PIN diode is used as the variable impedance component. It is often used in high frequency switch (i.e. microwave switch), phase modulation, limiter and other circuits. 12. Avalanche diodes (Avalanche Diode) which is the applied voltage can be generated under the action of high frequency oscillation transistor. High-frequency oscillation Luan works: the use of avalanche breakdown of the crystal injected carriers due to the transit wafer carriers require some time, so the current lags the voltage, a delay time, if properly controlled transition The more time, then the relationship between the current and voltage will appear on the negative resistance effect, thereby generating high frequency oscillation. It is often used in the field of microwave oscillation circuit. 13 Esaki diode (Tunnel Diode) which is based on tunneling current is the main current component of the crystal diode. Its base material is gallium arsenide and germanium. The N-type region of P-type doped region is a high (i.e., high concentration of impurities). Tunneling current is determined by these degenerate semiconductor quantum mechanical effects arising. Tunnel effect occurs with the following three conditions: ① the Fermi level in the conduction band and full-band; ② space charge layer width to be very narrow (0.01 micron); degenerate semiconductor P-type and N-type region of the hole and electronics on the same level with the possibility of overlap. Esaki diode is a two-terminal active device. The main parameters are peak current ratio (IP / PV), where the subscript "P" stands for "peak"; while the subscript "V" stands for "valley." Esaki diode can be used in low noise amplifiers and high-frequency oscillator (its operating frequency up to millimeter wavelengths), can also be used in high speed switching circuits. 14 Quick Shutdown (step recovery) diode (Step Recovary Diode) It is also a kind of a PN junction diode. Its structure is characterized by: at the boundary of the PN junction with a steep impurity distribution, thereby forming a "self-field." Since PN junction under forward bias, conducting the minority carriers, and the PN junction near a charge storage effect, to reverse the current to go through a "storage time" in order to reduced the minimum value ( reverse saturation current value). Step recovery diode "self-field" shorten storage time, so that the reverse current fast deadlines and produce a rich harmonic component. These harmonic components may be designed using the comb spectrum generating circuit. Fast turn-off (step recovery) diodes for pulsed and high harmonic circuit. 15 Schottky diode; (Schottky Barrier Diode)diode circuit
It is a Schottky characteristics of the "metal-semiconductor junction" diode. Its forward starting voltage is low. In addition to the metal layer material, you can also use gold, molybdenum, nickel, titanium and other materials. The semiconductor material of silicon or gallium arsenide, mostly N-type semiconductor. This device is a majority carrier conduction, so compared to the reverse saturation current of minority carriers of the PN junction greater conductivity. Schottky diode as minority carriers minimal memory effect, so the frequency response of the RC time constant is only limited, hence, it is ideal for high and fast switching device. The operating frequency of up to 100GHz. And, MIS (Metal - Insulator - Semiconductor) Schottky diode can be used to produce solar cells or light-emitting diodes. As a freewheeling diode, inductor in switching power supplies and relays and other inductive loads freewheeling role to play. 16. Damper diode damper diode is used in the high-frequency voltage circuit, with higher reverse voltage and peak current, forward voltage drop is small, high frequency high voltage rectifier diodes, used in the television line scan circuit for damping and step rectifier. Common damping diode has 2CN1, 2CN2, BSBS44 so on. 17 transient voltage suppression diodes TVP tube for fast overvoltage protection circuit, sub-type two bipolar and unipolar, press peak power (500W-5000W) and voltage (8.2V ~ 200V) classification. 18 double-base diode (single-junction transistor) two base, an emitter of the three-terminal negative resistance device for relaxation oscillator circuit, the timing voltage readout circuit,R4i SDHC, it has easy to tune the frequency, temperature stability and good advantages. 19 GaP light-emitting diode, GaAsP materials, small, positively driven to emit light. Low operating voltage, operating current is small, light uniformity, long life, red, yellow, green, and blue monochromatic light. As technology advances, the recent development has become more bright white light diodes, LED lighting formation of this emerging industry. Also used in VCD, DVD, calculator display. 20, Silicon Power Silicon Switching Diode high power switching diodes have the ability to turn on and off. It is mainly used for high-power switch or regulator circuit, the DC-DC converter, high-speed motor speed and the driver circuit for high frequency rectification and freewheeling clamping, with soft recovery characteristics, strong overload, are widely used in computer , radar power supply, stepper motor control and other aspects. Edit this paragraph classification point contact diode characteristics, according to the forward and reverse characteristics are classified as follows. 1 point contact diode general use as the title of this diode, as said, is usually used in the detection and rectifying circuit, the forward and reverse characteristics are neither particularly good, the intermediate product is not particularly bad. Such as: SD34, SD46, 1N34A, etc. fall into this category. (2) high point contact diode reverse voltage is the maximum peak reverse voltage Maximum DC reverse voltage and high product. Using the high voltage detection circuit and the rectifier. This type of diode forward characteristics generally not very good or average. In the point-contact type germanium diode, a SD38, 1N38A, OA81 so. The germanium diode, the pressure is limited. Demanding when silicon alloys and diffusion. 3 high reverse resistance point contact diode forward voltage diode characteristics and the same general use. Although its reverse breakdown voltage is particularly high, but the reverse current is small, so its specialty is reverse resistance is high. Using the high input impedance circuit and the resistance load resistance of the circuit, the high reverse resistance type germanium diode, SD54, 1N54A etc. belong to this diode. 4 point contact diode high conductivity and high reverse resistance type it opposite. Despite its reverse characteristic is poor, but the forward resistance becomes sufficiently small. High point contact diode conduction, there are SD56, 1N56A and so on. Key type diode for high conductivity, the more excellent characteristics can be obtained. Such diodes, particularly in the load resistance is low, a high rectification efficiency. Edit this paragraph diode electrical properties is the single most important characteristic of the direction of conductivity. In the circuit, current can only flow from the diode cathode, anode flow. 1. 2. 3. 2. 2. 2.