Semiconductor diodes presentation. Parallel OOS for current

Presentation on the topic: semiconductor devices

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The rapid development and expansion of the fields of application of electronic devices is due to the improvement of the element base, which is based on semiconductor devices. Semiconductor materials in their resistivity (ρ = 10-6 ÷ 1010 Ohm m) occupy an intermediate place between conductors and dielectrics. The rapid development and expansion of the fields of application of electronic devices is due to the improvement of the element base, which is based on semiconductor devices. Semiconductor materials in their resistivity (ρ = 10-6 ÷ 1010 Ohm m) occupy an intermediate place between conductors and dielectrics.

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For the manufacture of electronic devices, solid semiconductors with a crystalline structure are used. For the manufacture of electronic devices, solid semiconductors with a crystalline structure are used. Semiconductor devices are devices whose operation is based on the use of the properties of semiconductor materials.

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Semiconductor diodes This is a semiconductor device with one p-n-junction and two leads, the operation of which is based on the properties of the p-n-junction. The main property of the p-n junction is one-sided conductivity - the current flows only in one direction. Conventional graphic designation (UGO) of the diode has the shape of an arrow, which indicates the direction of current flow through the device. Structurally, the diode consists of a p-n-junction enclosed in a case (except for micromodular open-frame ones) and two leads: from the p-region - the anode, from the n-region - the cathode. Those. a diode is a semiconductor device that passes current in only one direction - from the anode to the cathode. The dependence of the current through the device on the applied voltage is called the current-voltage characteristic (VAC) of the device I = f (U).

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Transistors A transistor is a semiconductor device designed to amplify, generate and convert electrical signals, as well as switch electrical circuits. A distinctive feature of the transistor is the ability to amplify voltage and current - the voltages and currents acting at the input of the transistor lead to the appearance of significantly higher voltages and currents at its output. The transistor got its name from the abbreviation of two English words tran (sfer) (re) sistor - controlled resistor. The transistor allows you to regulate the current in the circuit from zero to the maximum value.

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Classification of transistors: Classification of transistors: - according to the principle of operation: field (unipolar), bipolar, combined. - by the value of the dissipated power: low, medium and high. - by the value of the limiting frequency: low, medium, high and ultrahigh frequency. - by the value of the operating voltage: low and high voltage. - by functional purpose: universal, amplifying, key, etc. - by design: unpackaged and in case design, with rigid and flexible leads.

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Depending on the functions performed, transistors can operate in three modes: Depending on the functions performed, transistors can operate in three modes: 1) Active mode - used to amplify electrical signals in analog devices. The resistance of the transistor changes from zero to the maximum value - they say the transistor "opens" or "closes". 2) Saturation mode - the resistance of the transistor tends to zero. In this case, the transistor is equivalent to a closed relay contact. 3) Cut-off mode - the transistor is closed and has a high resistance, i.e. it is equivalent to an open relay contact. Saturation and cutoff modes are used in digital, pulse and switching circuits.

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Indicator An electronic indicator is an electronic indicating device designed for visual monitoring of events, processes and signals. Electronic indicators are installed in various household and industrial equipment to inform a person about the level or value of various parameters, for example, voltage, current, temperature, battery charge, etc. An electronic indicator is often mistakenly referred to as a mechanical indicator with an electronic scale.

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Presentation on the topic: Diode

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Tunnel diode. The first work confirming the reality of the creation of tunneling devices was devoted to the tunneling diode, also called the Esaki diode, and was published by L. Esaki in 1958. While studying the internal field emission in a degenerate germanium p-n junction, Esaki discovered an "anomalous" I – V characteristic: the differential resistance in one of the sections of the characteristic was negative. He explained this effect using the concept of quantum mechanical tunneling and at the same time obtained acceptable agreement between theoretical and experimental results.

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Tunnel diode. A tunnel diode is a semiconductor diode based on a p + -n + junction with heavily doped regions, in the straight section of the current-voltage characteristic of which an n-shaped dependence of current on voltage is observed. As is known, impurity energy bands are formed in semiconductors with a high concentration of impurities. In n-semiconductors, such a band overlaps with the conduction band, and in p-semiconductors, with the valence band. As a result, the Fermi level in n-semiconductors with a high concentration of impurities lies above the level Ec, and in p-semiconductors below the level Ev. As a result, within the energy range DE = Ev-Ec, any energy level in the conduction band of an n-semiconductor can correspond to the same energy level behind the potential barrier, i.e. in the valence band of a p-semiconductor.

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Tunnel diode. Thus, particles in n and p semiconductors with energy states within the DE interval are separated by a narrow potential barrier. In the valence band of the p-semiconductor and in the conduction band of the n-semiconductor, some of the energy states in the DE range are free. Consequently, through such a narrow potential barrier, on both sides of which there are unoccupied energy levels, tunnel motion of particles is possible. When approaching the barrier, the particles undergo reflection and return in most cases back, but there is still a probability of detecting a particle behind the barrier, as a result of the tunnel transition, the tunneling current density is nonzero and the density of the tunneling current is j t0. Let's calculate the geometric width of the degenerate p-n junction. We will assume that the asymmetry of the p-n junction is preserved in this case (p + is the heavily doped region). Then the width of the p + -n + transition is small: We estimate the Debroille wavelength of the electron from simple relations:

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Tunnel diode. The geometric width of the p + -n + junction turns out to be comparable to the de Broglie wavelength of the electron. In this case, the manifestation of quantum mechanical effects can be expected in the degenerate p + –n + junction, one of which is tunneling through a potential barrier. With a narrow barrier, the probability of tunnel seepage through the barrier is nonzero !!!

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Tunnel diode. Tunnel diode currents. In a state of equilibrium, the total current through the junction is zero. When a voltage is applied to the junction, electrons can tunnel from the valence band to the conduction band or vice versa. For the tunneling current to flow, the following conditions must be met: 1) the energy states on the side of the junction from which electrons tunnel must be filled; 2) on the other side of the transition, energy states with the same energy must be empty; 3) the height and width of the potential barrier should be small enough for a finite probability of tunneling to exist; 4) the quasimomentum must be conserved. Tunnel diode.swf

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Tunnel diode. Voltages and currents characterizing the singular points of the I - V characteristic are used as parameters. The peak current corresponds to the maximum of the I – V characteristic in the region of the tunneling effect. Voltage Uп corresponds to current Iп. The trough current Iv and Uv characterize the I – V characteristic in the region of the current minimum. The voltage of the solution Upp corresponds to the value of the current Ip on the diffusion branch of the characteristic. The falling section of the dependence I = f (U) is characterized by a negative differential resistance rД = -dU / dI, the value of which, with some error, can be determined by the formula

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Reversed diodes. Let us consider the case when the Fermi energy in electronic and hole semiconductors coincides or is at a distance ± kT / q from the bottom of the conduction band or the top of the valence band. In this case, the current-voltage characteristics of such a diode with a reverse bias will be exactly the same as that of a tunnel diode, that is, with an increase in the reverse voltage, there will be a rapid increase in the reverse current. As for the forward bias current, the tunneling component of the I – V characteristic will be completely absent due to the fact that there are no completely filled states in the conduction band. Therefore, with forward bias in such diodes up to voltages greater than or equal to half the bandgap, there will be no current. From the point of view of a rectifier diode, the current-voltage characteristic of such a diode will be inverse, that is, there will be high conductivity with reverse bias and low with forward bias. In this regard, this type of tunneling diodes are called inverted diodes. Thus, a reversed diode is a tunnel diode without a negative differential resistance section. The high nonlinearity of the current-voltage characteristic at low voltages near zero (on the order of microvolts) makes it possible to use this diode for detecting weak signals in the microwave range.

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Transient processes. With rapid changes in the voltage across a semiconductor diode based on a conventional p-n junction, the current through the diode corresponding to the static current-voltage characteristic is not immediately established. The process of establishing current during such switching is usually called a transient process. Transient processes in semiconductor diodes are associated with the accumulation of minority carriers in the base of the diode during its direct connection and their resorption in the base with a rapid change in the polarity of the voltage across the diode. Since there is no electric field in the base of an ordinary diode, the movement of minority carriers in the base is determined by the laws of diffusion and occurs relatively slowly. As a result, the kinetics of carrier accumulation in the base and their resorption affect the dynamic properties of diodes in the switching mode. Consider the changes in current I when the diode is switched from forward voltage U to reverse voltage.

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Transient processes. In the stationary case, the current in the diode is described by the equation After the completion of the transient processes, the current in the diode will be equal to J0. Consider the kinetics of the transient, that is, the change in the current of the pn junction when switching from forward voltage to reverse voltage. When the diode is forward biased based on an asymmetric pn junction, nonequilibrium holes are injected into the base of the diode. The time and space variation of nonequilibrium injected holes in the base is described. the equation of continuity:

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Transient processes. At the moment of time t = 0, the distribution of injected carriers in the base is determined from the diffusion equation and has the form: From the general provisions, it is clear that at the moment of switching the voltage in the diode from forward to reverse, the reverse current will be significantly higher than the thermal current of the diode. This will happen because the reverse current of the diode is due to the drift component of the current, and its value, in turn, is determined by the concentration of minority carriers. This concentration is significantly increased in the base of the diode due to the injection of holes from the emitter and is described at the initial moment by the same equation.

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Transient processes. Over time, the concentration of nonequilibrium carriers will decrease; therefore, the reverse current will also decrease. During the time t2, called the recovery time of the reverse resistance, or the absorption time, the reverse current will come to a value equal to the thermal current. To describe the kinetics of this process, we write the boundary and initial conditions for the continuity equation in the following form. At time t = 0, the equation for the distribution of injected carriers in the base is valid. When a stationary state is established at a time instant, the stationary distribution of nonequilibrium carriers in the base is described by the relation:

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Transient processes. The reverse current is due only to the diffusion of holes to the boundary of the space charge region of the p-n junction: The procedure for finding the kinetics of the reverse current is as follows. Taking into account the boundary conditions, the continuity equation is solved and the dependence of the concentration of nonequilibrium carriers in the base p (x, t) on time and coordinate is found. The figure shows the coordinate dependences of the concentration p (x, t) at different times. Coordinate dependences of the concentration p (x, t) at different times

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Transient processes. Substituting the dynamic concentration p (x, t), we find the kinetic dependence of the reverse current J (t). The dependence of the reverse current J (t) has the following form: Here is the additional error distribution function equal to The first expansion of the additional error function has the form: Let us expand the function in a series in cases of small and large times: t> p. We get: From this ratio it follows that at the moment t = 0 the value of the reverse current will be infinitely large. The physical limitation for this current will be the maximum current that can flow through the ohmic resistance of the diode base rB at a reverse voltage U. The magnitude of this current, called the cutoff current Jav, is equal to: Jav = U / rB. The time during which the reverse current is constant is called the cutoff time.

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Transient processes. For pulse diodes, the cutoff time τav and the recovery time τw of the reverse resistance of the diode are important parameters. There are several ways to decrease their value. First, the lifetime of nonequilibrium carriers in the base of the diode can be reduced by introducing deep recombination centers in the quasineutral volume of the base. Second, you can make the base of the diode thin so that nonequilibrium carriers recombine on the back side of the base.

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Electron-hole transition. Transistor

An electron-hole junction (or n - p junction) is the contact region of two semiconductors with different types of conductivity.

When two semiconductors of n and p types come into contact, the process of diffusion begins: holes from the p-region pass into the n-region, and electrons, on the contrary, from the n-region to the p-region. As a result, in the n-region near the contact zone, the concentration of electrons decreases and a positively charged layer appears. In the p-region, the hole concentration decreases and a negatively charged layer appears. At the semiconductor boundary, an electric double layer is formed, the electric field of which prevents the process of diffusion of electrons and holes towards each other.

The boundary region between semiconductors with different types of conductivity (blocking layer) usually reaches a thickness of the order of tens and hundreds of interatomic distances. The space charges of this layer create a blocking voltage U s between the p and n regions, which is approximately equal to 0.35 V for germanium n – p junctions and 0.6 V for silicon junctions.

Under conditions of thermal equilibrium in the absence of an external electric voltage, the total current through the electron-hole junction is zero.

If the n - p junction is connected to the source so that the positive pole of the source is connected to the p region, and the negative pole to the n region, then the electric field strength in the blocking layer will decrease, which facilitates the transition of the majority carriers through the contact layer. Holes from the p-region and electrons from the n-region, moving towards each other, will cross the n - p -junction, creating a current in the forward direction. The current through the n - p junction in this case will increase with increasing source voltage.

If a semiconductor with an n - p junction is connected to a current source so that the positive pole of the source is connected to the n region and the negative pole to the p region, then the field strength in the blocking layer increases. Holes in the p-region and electrons in the n-region will be displaced from the n - p -junction, thereby increasing the concentration of minority carriers in the blocking layer. There is practically no current through the n - p junction. A very insignificant reverse current is due only to the intrinsic conductivity of semiconductor materials, i.e., the presence of a small concentration of free electrons in the p-region and holes in the n-region. The voltage applied to the n - p -junction in this case is called reverse.

The ability of an n - p junction to pass current in almost only one direction is used in devices called semiconductor diodes. Semiconductor diodes are made from silicon or germanium crystals. In their manufacture, an impurity providing a different type of conductivity is fused into a crystal with some type of conductivity. Semiconductor diodes have many advantages over vacuum diodes - small size, long service life, mechanical strength. A significant disadvantage of semiconductor diodes is the dependence of their parameters on temperature. Silicon diodes, for example, can only work satisfactorily over a temperature range of –70 ° C to 80 ° C. For germanium diodes, the operating temperature range is somewhat wider.

Semiconductor devices with not one, but two n - p junctions are called transistors. The name comes from a combination of English words: transfer - to transfer and resistor - resistance. Usually germanium and silicon are used to create transistors. There are two types of transistors: p - n - p transistors and n - p - n transistors.

The p - n - p germanium transistor is a small plate made of germanium with a donor impurity, that is, from an n-type semiconductor. In this plate, two regions with an acceptor impurity are created, i.e., regions with hole conduction.

In an n - p - n-type transistor, the main germanium plate has a p-type conductivity, and the two regions created on it have an n-type conductivity.

The plate of the transistor is called the base (B), one of the regions with the opposite type of conductivity is called the collector (K), and the second is the emitter (E). Typically, the volume of the collector is greater than the volume of the emitter.

In the legend of the different structures, the emitter arrow shows the direction of the current through the transistor.

Inclusion of a p - n - p -structure transistor in the circuit The "emitter-base" transition is switched on in the forward (throughput) direction (emitter circuit), and the "collector-base" transition - in the blocking direction (collector circuit).

When the emitter circuit is closed, the holes - the main charge carriers in the emitter - pass from it to the base, creating a current I e in this circuit. But for holes that have entered the base from the emitter, the n - p junction in the collector circuit is open. Most of the holes are captured by the field of this transition and penetrate into the collector, creating a current I to.

In order for the collector current to be practically equal to the emitter current, the base of the transistor is made in the form of a very thin layer. When the current in the emitter circuit changes, the current in the collector circuit also changes.

If an alternating voltage source is connected to the emitter circuit, then an alternating voltage also appears across the resistor R connected to the collector circuit, the amplitude of which can be many times greater than the amplitude of the input signal. Therefore, the transistor acts as an AC voltage amplifier.

However, such a transistor amplifier circuit is ineffective, since there is no current amplification of the signal in it, and the entire emitter current I e flows through the input signal sources. In real transistor amplifier circuits, an alternating voltage source is switched on so that only a small base current I b = I e - I k flows through it. Small changes in the base current cause significant changes in the collector current. The current gain in such circuits can be several hundred.

Currently, semiconductor devices are widely used in radio electronics. Modern technology makes it possible to produce semiconductor devices - diodes, transistors, semiconductor photodetectors, etc. - several micrometers in size. A qualitatively new stage in electronic technology was the development of microelectronics, which is engaged in the development of integrated microcircuits and the principles of their application.

An integrated microcircuit is a combination of a large number of interconnected elements - ultra-small diodes, transistors, capacitors, resistors, connecting wires, made in a single technological process on a single crystal. A microcircuit with a size of 1 cm 2 can contain several hundred thousand microelements. The use of microcircuits has led to revolutionary changes in many areas of modern electronic technology. This is especially evident in the field of electronic computing. Bulky computers containing tens of thousands of electronic tubes and occupying entire buildings were replaced by personal computers.

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Diode - vacuum or semiconductor devices that transmit alternating electric current in only one direction and have two contacts for inclusion in an electrical circuit.

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A diode has two contacts called an anode and a cathode. When a diode is connected to an electrical circuit, the current flows from the anode to the cathode. The ability to conduct current only in one direction is the main property of a diode. Diodes belong to the class of semiconductors and are considered active electronic components (resistors and capacitors are passive).

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One-sided conductivity of a diode is its main property. This property determines the purpose of the diode: - conversion of high-frequency modulated oscillations into audio-frequency currents (detection); - AC to DC rectification Diode properties

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Classification of diodes According to the initial semiconductor material, diodes are divided into four groups: germanium, silicon, from gallium arsenide and indium phosphide. Germanium diodes are widely used in transistor receivers, as they have a higher transmission coefficient than silicon ones. This is due to their higher conductivity at a low voltage (about 0.1 ... 0.2 V) of a high-frequency signal at the detector input and a relatively low load resistance (5 ... 30 kOhm). Semiconductor diodes

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By design and technology, there are point and plane diodes. According to their intended purpose, semiconductor diodes are divided into the following main groups: rectifier, universal, pulse, varicaps, zener diodes (reference diodes), stabilizers, tunnel diodes, inverted diodes, avalanche-transit (LPD), thyristors, photodiodes, LEDs and optocouplers.

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Diodes are characterized by the following basic electrical parameters: - the current passing through the diode in the forward direction (forward current Ipr); - by the current passing through the diode in the opposite direction (reverse current Iobr); - the highest permissible rectified CURRENT rectified. Max; - the highest permissible direct current І pr.dop .; - direct voltage U n p; - reverse voltage and about P; - the highest permissible reverse voltage and obr.max - capacitance SD between the diode terminals; - dimensions and operating temperature range

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Correct polarity must be observed when connecting the diode to the circuit. To make it easy to determine the location of the cathode and anode, special marks are applied to the body or one of the terminals of the diode. There are various ways of marking diodes, but most often an annular strip is applied to the side of the case corresponding to the cathode. If there is no diode marking, then the terminals of the semiconductor diodes can be determined using a measuring device - the diode passes current only in one direction.

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The operation of a diode can be visualized with a simple experiment. If a battery is connected to the diode through a low-power incandescent lamp so that the positive terminal of the battery is connected to the anode, and the negative terminal to the cathode of the diode, then a current will flow in the resulting electrical circuit and the lamp will light up. The maximum value of this current depends on the resistance of the diode's semiconductor junction and the DC voltage applied to it. This state of the diode is called open, the current flowing through it is the direct current Ipr, and the voltage applied to it, due to which the diode is in the open, is the direct voltage Upr. If the leads of the diode are reversed, then the lamp will not glow, since the diode will be in a closed state and present a strong resistance to the current in the circuit. It is worth noting that a small current through the semiconductor junction of the diode will still flow in the opposite direction, but in comparison with the forward current it will be so small that the light bulb will not even react. Such a current is called the reverse current Irev, and the voltage that creates it is called the reverse voltage Urev.

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Diode marking The diode body usually indicates the material of the semiconductor from which it is made (letter or number), type (letter), purpose or electrical properties of the device (number), the letter corresponding to the type of device, and the date of manufacture, as well as its symbol. The diode symbol (anode and cathode) indicates how to connect the diode on the device boards. The diode has two leads, one of which is the cathode (minus) and the other is the anode (plus). A conventional graphic image on the diode body is applied in the form of an arrow indicating the forward direction, if there is no arrow, then a "+" sign is put. On the flat terminals of some diodes (for example, the D2 series), the symbol of the diode and its type are directly stamped. When applying a color code, a color mark, dot or strip is applied closer to the anode (Figure 2.1). For some types of diodes, color marking in the form of dots and stripes is used (Table 2.1). Diodes of old types, in particular point ones, were produced in glass design and were marked with the letter "D" with the addition of a number and a letter denoting the subtype of the device. Germanium-indium planar diodes were designated "D7".

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Designation system The designation system consists of four elements. The first element (letter or number) indicates the original semiconductor material from which the diode is made: G or 1 - germanium * K or 2 - silicon, A or 3 - gallium arsenide, And or 4 - indium phosphide. The second element is a letter indicating the class or group of the diode. The third element is a number that defines the purpose or electrical properties of the diode. The fourth element indicates the serial number of the technological development of the diode and is designated from A to Z. For example, the KD202A diode stands for: K - material, silicon, D - rectifier diode, 202 - purpose and development number, A - variety; 2S920 - high-power silicon zener diode, type A; AIZ01B is an indium-phosphide tunneling diode of the switching type B. Sometimes there are diodes designated according to outdated systems: DG-Ts21, D7A, D226B, D18. D7 diodes differ from DG-Ts diodes in an all-metal housing design, as a result of which they work more reliably in a humid atmosphere. Germanium diodes of the DG-Ts21 ... DG-Ts27 type and diodes D7A ... D7Zh, close to them in characteristics, are usually used in rectifiers to power radio equipment from an alternating current network. The diode symbol does not always include some technical data, so they must be looked for in reference books on semiconductor devices. One of the exceptions is the designation for some diodes with the letters KS or a number instead of K (for example, 2C) - silicon zener diodes and stabilizers. After these designations there are three digits, if these are the first digits: 1 or 4, then taking the last two digits and dividing them by 10 we get the stabilization voltage Ust. For example, KS107A is a stabilizer, Ust = 0.7 V, 2C133A is a zener diode, Ust = 3.3 V. If the first digit is 2 or 5, then the last two digits show Ust, for example, KS 213B - Ust = 13 V, 2C 291A - 0Ust = 91 V, if the digit is 6, then 100 V must be added to the last two digits, for example, KS 680A - Ust = 180 V.

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Block diagram of a semiconductor diode with p - n-junction: 1 - crystal; 2 - conclusions (current leads); 3 - electrodes (ohmic contacts); 4 - plane of p - n-junction. Typical current-voltage characteristic of a semiconductor diode with a p - n-junction: U - voltage across the diode; I is the current through the diode; U * obr and I * obr - the maximum allowable reverse voltage and the corresponding reverse current; Ucт - stabilization voltage.

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Small-signal (for low signal levels) equivalent circuit of a semiconductor diode with a p - n-junction: rp-n - nonlinear resistance of the p-n-junction; rb - resistance of the semiconductor volume (diode base); ryт - surface leakage resistance; СБ - barrier capacity of p - n-junction; Sdif - diffusion capacity due to the accumulation of mobile charges in the base at forward voltage; CK - the capacity of the case; Lк - inductance of current leads; A and B are conclusions. The solid line shows the connection of elements related to the actual p - n-junction. Volt-ampere characteristics of the tunnel (1) and reversed (2) diodes: U - voltage across the diode; I - current through the diode

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Semiconductor diodes (appearance): 1 - rectifier diode; 2 - photodiode; 3 - microwave diode; 4 and 5 - diode matrices; 6 - pulse diode. Diode cases: 1 and 2 - metal-glass; 3 and 4 - metal-ceramic; 5 - plastic; 6 - glass

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Schottky diode Schottky diodes have a very low voltage drop and are faster than conventional diodes. Zener diode / Zener diode / Zener diode prevents the voltage from exceeding a certain threshold in a specific section of the circuit. It can perform both protective and limiting functions, they work only in DC circuits. When connecting, observe the polarity. The same type of zener diodes can be connected in series to increase the stabilized voltage or form a voltage divider. Varicap A varicap (otherwise a capacitive diode) changes its resistance depending on the voltage applied to it. It is used as a controlled variable capacitor, for example, for tuning high-frequency oscillatory circuits.

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Thyristor A thyristor has two stable states: 1) closed, that is, a state of low conductivity, 2) open, that is, a state of high conductivity. In other words, it is capable of moving from a closed state to an open state under the action of a signal. The thyristor has three outputs, in addition to the Anode and Cathode, there is also a control electrode - it is used to transfer the thyristor into the on state. Modern imported thyristors are also produced in TO-220 and TO-92 cases. Thyristors are often used in circuits for power control, for smooth starting of motors or turning on light bulbs. Thyristors allow high currents to be controlled. For some types of thyristors, the maximum forward current reaches 5000 A or more, and the voltage value in the off-state is up to 5 kV. Powerful power thyristors of the T143 (500-16) type are used in control cabinets for electric motors, frequency drives

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Infrared diode Infrared LEDs (abbreviated as IR diodes) emit light in the infrared range. The fields of application of infrared LEDs are optical instrumentation, remote control devices, optocoupler switching devices, and wireless communication lines. IR diodes are identified in the same way as LEDs. Infrared diodes emit light outside the visible range, the glow of the IR diode can be seen and viewed, for example, through a cell phone camera, these diodes are also used in CCTV cameras, especially on street cameras so that the picture is visible at night. Photodiode A photodiode converts light that hits its photosensitive area into an electric current, and is used in converting light into an electrical signal.

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Semiconductor diodes presentation. Parallel OOS for current

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