What a diode. What is a diode: definition, features, circuit and application

Hello everyone!

In this article, we will analyze the principle of operation of a semiconductor device such as a DIOD.

Let's start in order.

So, diode- this, which, in simple terms, one side (in the forward direction) passes the current well, and the other (that is, in the opposite direction) badly. Diode has two leads: positive - anode and negative - cathode.

I will say right away that in the design of almost every (99.99%) electronic device there is a diode or diodes.

This semiconductor device is used as a rectifier. For example, using a diode bridge, which consists of four diodes, you can rectify an alternating current and it will become constant. If you use six diodes, then you can turn a three-phase voltage into a single-phase one. Diodes are used in power supplies, in various audio and video devices, telephones and many other places.

If you connect the diode to a power source, the output voltage will differ from the initial one by 0.5 ... 0.7 V. For a smaller voltage drop, Schottky diodes are used, in this case the voltage drop will be about 0.1 V.

Diode device shown in the figure below:

1 - crystal, 2 - conductors (leads), 3 - electrodes, 4 - plane p-ntransition.

Diode crystals are made mainly of silicon or germanium. One region of the crystal has a p-type conductivity (hole, has an artificially created lack of electrons), the other contains an excess of electrons and has an n-type conductivity. The border between areas is called a p-n junction. In Latin, the letter p begins the word "positive", and the letter n begins the word "negative". Direct connection of a diode is called connecting a positive voltage to the anode, and negative to the cathode. In this connection, the diode is open. If you connect it the other way around, then the diode will be closed and no current will pass. This connection is called "reverse". The reverse resistance of the diode is very high; in circuits it is used as an insulator (or dielectric).

Watch over diode operation you can do that.

You need to take a power source, an incandescent lamp and, in fact, a diode. Putting together a simple scheme:

"Plus" of the power supply is connected to the anode of the diode, "minus" to one terminal of the lamp. We connect the cathode of the diode to the second terminal of the lamp. In this "direct" connection, the lamp will glow. Now let's turn the diode over, i.e. let's make a "reverse" connection. In such a connection, the lamp will not glow, since the transition is closed.

D iodine- the simplest device in the glorious family of semiconductor devices. If we take a semiconductor plate, for example germanium, and introduce an acceptor impurity into its left half, and into the right donor one, then on one side we get a semiconductor of type P, respectively, on the other side of type N. In the middle of the crystal we get the so-called P-N transition as shown in Figure 1.

The same figure shows the conventional graphic designation of the diode in the diagrams: the output of the cathode (negative electrode) is very similar to the "-" sign. It's easier to remember that way.

In total, such a crystal has two zones with different conductivity, from which two leads come out, therefore the resulting device was named diode because the prefix "di" means two.

In this case, the diode turned out to be a semiconductor, but similar devices were known before: for example, in the era of vacuum tubes there was a tube diode called the kenotron. Now such diodes have become history, although adherents of the "tube" sound believe that in a tube amplifier even an anode voltage rectifier should be a tube!

Figure 1. The structure of the diode and the designation of the diode in the diagram

At the junction of semiconductors with P and N conductivities, we obtain P-N junction, which is the basis of all semiconductor devices. But unlike a diode, which has only one transition, they have two P-N transitions, and, for example, consist of four transitions at once.

P-N transition at rest

Even if the P-N junction, in this case a diode, is not connected anywhere, interesting physical processes still occur inside it, which are shown in Figure 2.

Figure 2. Diode at rest

There is an excess of electrons in the N region, it carries a negative charge, and in the P region, the charge is positive. Together, these charges form an electric field. Since opposite charges tend to attract, electrons from the N zone penetrate into the positively charged P zone, filling some holes. As a result of this movement inside the semiconductor, a current, albeit very small (units of nanoamperes), arises.

As a result of this movement, the density of the substance on the P side increases, but up to a certain limit. Particles usually tend to spread evenly throughout the entire volume of a substance, just like the smell of perfume spreads throughout a room (diffusion), therefore, sooner or later, electrons return back to the N zone.

If for most consumers of electricity the direction of the current does not matter - the light is on, the tile is warming up, then for the diode the direction of the current plays a huge role. The main function of a diode is to conduct current in one direction. It is this property that is provided by the P-N transition.

Turning on the diode in the opposite direction

If you connect a power supply to the semiconductor diode, as shown in Figure 3, then the current will not pass through the P-N junction.

Figure 3. Reverse connection of the diode

As you can see in the figure, the positive pole of the power supply is connected to the N area, and the negative pole to the P area. As a result, electrons from the N region rush to the positive pole of the source. In turn, positive charges (holes) in the P region are attracted by the negative pole of the power source. Therefore, in the region of the P-N junction, as can be seen in the figure, a void is formed, there is simply nothing to conduct the current, there are no charge carriers.

With an increase in the voltage of the power source, electrons and holes are more and more attracted by the electric field of the battery, while in the region of the P-N transition there are less and less charge carriers. Therefore, in the reverse connection, the current does not flow through the diode. In such cases, it is customary to say that the semiconductor diode is reverse voltage locked.

An increase in the density of the substance near the poles of the battery leads to the occurrence of diffusion, - the desire for a uniform distribution of matter throughout the volume. This is what happens when the battery is disconnected.

Semiconductor diode reverse current

This is where the time has come to recall the minor media that were conventionally forgotten. The fact is that even in the closed state, an insignificant current, called reverse current, passes through the diode. This reverse current and is created by non-main carriers, which can move in the same way as the main ones, only in the opposite direction. Naturally, such a movement occurs under reverse voltage. The reverse current is generally low due to the small amount of minority carriers.

As the crystal temperature rises, the number of minority carriers increases, which leads to an increase in the reverse current, which can lead to the destruction of the P-N junction. Therefore, the operating temperatures for semiconductor devices - diodes, transistors, microcircuits are limited. In order to prevent overheating, powerful diodes and transistors are installed on heat sinks - radiators.

Forward diode turn-on

Shown in Figure 4.

Figure 4. Direct connection of a diode

Now let's change the polarity of switching on the source: connect the minus to the N region (cathode), and the plus to the P region (anode). With this inclusion in the N region, the electrons will be repelled from the minus of the battery, and move towards the P-N junction. In the P region, the positively charged holes will be repulsed from the positive terminal of the battery. Electrons and holes rush towards each other.

Charged particles with different polarities gather around the P-N junction, and an electric field arises between them. Therefore, the electrons overcome the P-N transition and continue to move through the P zone. In this case, some of them recombine with holes, but most of them rush to the plus of the battery, the current Id went through the diode.

This current is called direct current... It is limited by the technical data of the diode, some maximum value. If this value is exceeded, there is a danger of diode failure. However, it should be noted that the direction of the forward current in the figure coincides with the generally accepted, reverse motion of electrons.

It can also be said that in the forward direction of switching on, the electrical resistance of the diode is relatively small. With the reverse connection, this resistance will be many times greater, the current does not flow through the semiconductor diode (a slight reverse current is not taken into account here). From the foregoing, we can conclude that the diode behaves like an ordinary mechanical valve: turned in one direction - water flows, turned in the other - the flow stopped. For this property, the diode was named semiconductor valve.

To understand in detail all the abilities and properties of a semiconductor diode, you should get acquainted with its volt - ampere characteristic... It is also a good idea to learn about the various diode designs and frequency properties, the advantages and disadvantages. This will be discussed in the next article.

What is a diode? In order to answer this question, you need to dig deep into the very beginning, namely, where does a semiconductor begin.

Introduction from theory

Conductor

Let's try to imagine a piece of conductor material, such as copper. What is it characterized by: it has free charge carriers - electrons. Moreover, there are a lot of such negative particles in it.

If a plus is applied to this area, then all these negative elements will rush to it, that is, a current will flow through the copper. This is a well-known fact, therefore, it is copper that is used as conductive materials. Conductors also include such elements of the periodic table as aluminum, iron, gold and many others.

Dielectric

A dielectric is a material that has no free charge carriers and, therefore, does not conduct current.

Semiconductor

A semiconductor is both a metal and a non-metal. A material that is both conductive and non-conductive. It has few free charge carriers. Typical semiconductors are silicon, germanium.

What is a diode

Silicon is a tetravalent element. To turn it into a conductor, pentavalent arsenic is mixed with it. As a result of this connection, extra electrons appear, that is, free charge carriers. And if you add trivalent indium to silicon, positrons, particles with a lack of an electron, will appear in the material. The diode consists of such areas.

The resulting structure is called a PN element or PN junction. P is the positive part, N is the negative. One part of the material is enriched with positive positrons, the other with negative electrons.

How does a diode work

You can physically not see the diodes themselves, but the result of their action surrounds us everywhere. These devices allow you to control the flow of current in the specified direction. There are many different types of diodes. When is it necessary? Below we will consider examples and, to some extent, the principle of operation of semiconductor diodes.

If you add two metal plates to the P and N working areas of the material, you get the anode and cathode electrodes. The scheme for connecting the electrodes to the source can work as follows:

• supplying voltage from the battery to the N electrode ensures the attraction of positrons, respectively, to the P electrode - electrons;
• lack of voltage returns everything to its original state;
• The change in the polarity of the applied voltage ensures the attraction of electrons in the opposite direction to the plus plate, and positrons to the minus one.

In the latter case, excess charges accumulate on the metal plates, while a dead insulating zone forms in the center of the material itself. Thus, the central portion of the material becomes a dielectric. In this direction, the device does not pass current.

For information. The word comes from di (double) + -ode. The definition of the terms cathode and anode of a diode, referring to contacts, is known to everyone. The cathode is negative electrode, the anode is positive. If you apply a plus to the anode, and a minus to the cathode, then the diode will open, and the electric current will flow through it.

Thus, a diode is a device that has two electrodes: a cathode and an anode. A simple non-linear electronic device made up of two different semiconductors. How the diode works can be clearly seen in the image.

Diodes are semiconductors made up of the P and N regions. Due to the properties of the PN junction, the diode conducts current only in one direction. This is how these devices work. What are they for?

Purpose of diodes

Diodes are of various designs: from bulky Soviet ones to miniature modern ones. The device may be of the same power, but due to the release time, it may differ in size. Diodes for high current require cooling, therefore they are made with a mount for a radiator. Accordingly, devices without a heatsink are designed for low currents.

Application of diodes

Diode devices can be oriented towards limiting or stopping the movement of current. An extremely common application is its use as a rectifier.

Rectifiers

Since the diode only allows current to flow in one direction, only the positive or negative portion of the sine wave voltage passes through the diode. This means that it is possible to efficiently convert AC to DC by using diodes arranged in a full wave rectifier.

For example, there is an alternating current source. At the exit from it, a diode is put into the circuit through which the load is connected. What happens? If the source gives a sinusoid, then only a positive half-wave will pass at the output of the diode. And so on until the next half-wave. But if you turn the diode on the other side, then the output will be a negative half-wave, that is, the device passes current in only one direction.

If you put a bridge consisting of four diodes in place of the diode, then the output will be a signal in the form of half-waves, reminiscent of a camel's hump. The half-waves will all unfold in the same direction. When an additional capacitor is installed after the diodes, the same half-waves will be obtained, only smoothed.

Varicaps

The graphic icon of the varicap is very similar to the conventional image of a semiconductor diode. A varicap is an ordinary diode. The operation of the device is based on the dependence of the barrier capacity of the pn junction on the reverse voltage. If the voltage is applied small, the capacitance turns out to be large, if a large voltage is applied, the capacitance becomes small. In reality, varicaps change their capacity several times (up to 7 times).

Zener Diodes

A zener diode is a reverse-biased semiconductor diode in breakdown mode. A zener diode with a large margin of power dissipation is chosen, because it constantly operates in breakdown mode. The main purpose of zener diodes is voltage stabilization.

The main purpose of the voltage regulator is to maintain a constant voltage across the load, regardless of changes in input voltage and load current. Under varying load current conditions, a zener diode can be used to obtain a stabilized output voltage. This is the main reason for using a zener diode as a voltage regulator.

Schottky diodes

A Schottky diode is a low-voltage device that uses metal and an electron-rich semiconductor as electrodes. The voltage of such a diode is approximately 0.2-0.4 V, in comparison with a conventional diode, this value is two times less.

The area of ​​application of the Schottky diode is limited, since it cannot work without a zener diode. Basically, Schottky diodes are used in devices operating in low-voltage circuits with a reverse voltage of the order of units and several tens of volts.

LEDs

Light-emitting diodes are now widely used as diode blocks for light energy-saving light bulbs. They are becoming indispensable for people's lives, as they help to reduce the rising prices of electricity.

For information. Flashing LEDs are often used in various signal circuits to decorate the home interior. There are circuits that can be used to make the LEDs blink. Making blinking LEDs is a doable task.

Diode is- a semiconductor device that passes electrical current in only one direction.This is a very brief description of the diode's properties and operation and is the most accurate. Now let's figure it out in more detail, especially since with a diode you begin your acquaintance with a huge family of semiconductors.What is a semiconductor?From the very name of the semiconductor, it is clear that it is half-conductive. In a specific case, the diode passes electric current only in one direction and does not pass it in the opposite direction. Works as a nipple or spool system in a car or bicycle chamber. The air pumped by the pump through the spool or nipple enters the car chamber and does not come out back due to its locking by the spool. The figure shows a diode as it is indicated on electrical circuits.

In accordance with the figure, the triangle (anode) shows in which direction the electric current flows from plus to minus, the diode will be "open", respectively from the side of the vertical strip (cathode), the diode will be "locked".

This property of the diode is used to convert alternating current to direct current for this purpose, the diodes are collected diode bridge.

Diode bridge

How does a diode bridge work? The following figure shows a schematic diagram of a diode bridge. Please note that the input of the diode bridge is supplied alternating current, at the output we already get D.C. Now let's figure out how the conversion of alternating current to direct current occurs.

If you read my article "What is alternating current" you must remember that alternating current changes its direction with a certain frequency. Simply put, at the input terminals of the diode bridge, plus and minus will change places with the network frequency (in Russia, this frequency is 50 Hertz), which means (+) and (-) change places 50 times per second. Suppose in the first cycle on the terminal “A” there will be a positive potential (+) on the terminal “B” negative (-). The plus from terminal "A" can only pass in one direction along the red arrow, through the diode "D1" to the output terminal with a sign (+) and then through resistor (R1) through diode “D3” to minus terminals “B”. In the next cycle, when plus and minus are reversed, everything will happen exactly the opposite. Plus from terminal “B” through diode “D2” will pass to the output terminal with a sign (+) and then through resistor (R1) through diode “D4” to minus terminals “A”. Thus, we get a constant electric current at the input of the rectifier, which moves only in one direction from plus to minus (as in a conventional battery). This method of converting alternating current into direct current is used in all electronic devices that are powered from a 220V electrical network. In addition to diode bridges assembled from individual diodes, electronic components are used in which, for ease of installation, rectifier diodes are enclosed in one compact case. Such a device is called "Diode assembly".

Diodes are not only rectifier. There are diodes whose conductivity depends on the illumination they are called "Photodiodes" they are denoted as follows -

They may look like this -

LEDs, you are well aware, they are found in the Christmas tree garland and in powerful searchlights and headlights of cars. In the diagram, they are denoted as follows -

LEDs look like this -

How to check a diode

Verify diode you can use an ordinary multimeter - how to use a multimeter in this article, to check, we switch the tester to the dial mode. We connect the probes of the device to the diode electrodes, the black probe to the cathode

(on housings of modern diodes, the cathode is marked with a ring mark),we connect the red probe to the anode (as you already know, the diode passes voltage only in one direction)the resistance of the diode will be small i.e. the numbers on the instrument will make a big difference.

We switch the probes of the device in reverse -

The resistance will be very large and practically endless. If you succeed as I wrote, the diode is working, if in both cases the resistance is very large, then the “diode in the open circuit” is faulty and does not transmit voltage at all, if the resistance is very small, then the diode is broken and passes voltage in both directions.

How to check a diode bridge

If the diode bridge is made up of separate diodes, each diode is tested separately as described above. It is not necessary to solder each diode from the circuit, but it is better to disconnect the positive or negative terminal of the rectifier from the circuit.

If you need to check the diode assembly, where the diodes are in the same case and it is impossible to get to them, we proceed as follows,

We connect one probe multimerta to the plus of the diode assembly, and the second, in turn, touch the terminals of the assembly where the alternating current is supplied. In one direction, the device should show little resistance when changing probes in the opposite direction, very high resistance. Then we also check the rectifier with respect to the negative output. If the reading in both directions is small or large, the diode assembly is defective. This test method is used when electronics are being repaired.

High-frequency diodes, pulse, tunnel, varicaps, all these diodes are widely used in household and special equipment. In order to understand and figure out how to correctly use and where to use which diodes, you need to improve your knowledge, study special literature and, of course, do not hesitate to ask questions.

- an electronic device with two (sometimes three) electrodes, which has one-sided conductivity. The electrode connected to the positive pole of the device is called the anode, to the negative pole - the cathode. If a direct voltage is applied to the device, then it is in the open state, in which the resistance is small, and the current flows unhindered. If a reverse voltage is applied, the device is closed due to the high resistance. Reverse current is present, but it is so small that it is conventionally assumed to be zero.

General classification

Diodes are divided into large groups - non-semiconductor and semiconductor.

Non-semiconductor

One of the oldest varieties are lamp (vacuum) diodes... They are radio tubes with two electrodes, one of which is heated by a filament. In the open state, charges move from the surface of the heated cathode to the anode. With the opposite direction of the field, the device switches to the closed position and practically does not pass the current.

Another type of non-semiconductor devices - gas filled, of which only arc discharge models are used today. Gasotrons (devices with hot cathodes) are filled with inert gases, mercury vapor or vapors of other metals. Special oxide anodes used in gas-filled diodes are capable of withstanding high current loads.

Semiconductor

Semiconductor devices are based on the p-n junction principle. There are two types of semiconductors, p-type and n-type. For p-type semiconductors, an excess of positive charges is characteristic, for n-type semiconductors, an excess of negative charges (electrons). If semiconductors of these two types are located next to each other, then two narrow charged regions are located near the boundary separating them, which are called p-n junction. Such a device with two types of semiconductors with different impurity conductivity (or semiconductor and metal) and a pn junction is called semiconductor diode... It is semiconductor diode devices that are most in demand in modern devices for various purposes. For different areas of application, many modifications of such devices have been developed.

Semiconductor diodes

Types of diodes by junction size

According to the size and nature of the p-n junction, there are three types of devices - planar, point and microalloy.

Planar details represent one semiconductor plate in which there are two regions with different impurity conductivity. The most popular products are made from germanium and silicon. The advantages of such models are the ability to operate at significant direct currents, in conditions of high humidity. Due to their high barrier capacitance, they can only operate at low frequencies. Their main applications are in AC rectifiers installed in power supplies. These models are called rectifiers.

Point diodes have an extremely small p-n junction area and are adapted to work with low currents. They are called high-frequency because they are used mainly for converting modulated oscillations of significant frequency.

Microalloy models are obtained by fusing single crystals of p-type and n-type semiconductors. According to the principle of operation, such devices are planar, but in terms of characteristics they are similar to point ones.

Materials for making diodes

Silicon, germanium, gallium arsenide, indium phosphide, selenium are used in the production of diodes. The first three materials are the most common.

Purified silicon- a relatively inexpensive and easy-to-process material that is most widely used. Silicon diodes are excellent general purpose models. Their bias voltage is 0.7 V. In germanium diodes, this value is 0.3 V. Germanium is a rarer and more expensive material. Therefore, germanium devices are used in cases where silicon devices cannot effectively cope with a technical task, for example, in low-power and precision electrical circuits.

Types of diodes by frequency range

According to the operating frequency, the diodes are divided into:

• Low frequency - up to 1 kHz.
• High frequency and ultra high frequency - up to 600 MHz. At such frequencies, point-type devices are mainly used. The capacitance of the junction should be low - no more than 1-2 pF. They are effective in a wide range of frequencies, including low-frequency ones, therefore they are universal.
• Pulse diodes are used in circuits in which high speed is a fundamental factor. According to the manufacturing technology, such models are divided into point, alloy, welded, diffuse.

Diode Applications

Modern manufacturers offer a wide range of diodes tailored to specific applications.

Rectifier diodes

These devices serve to rectify an AC sinusoid. Their principle of operation is based on the property of the device to go into the closed state upon reverse bias. As a result of the operation of the diode device, the negative half-waves of the current sinusoid are cut off. According to the dissipation power, which depends on the highest allowed forward current, rectifier diodes are divided into three types - low-power, medium-power, powerful.

• Low current diodes can be used in circuits in which the current value does not exceed 0.3 A. Products are characterized by low weight and compact dimensions, since their body is made of polymer materials.
• Medium Power Diodes can operate in the range of currents 0.3-10.0 A. In most cases, they have a metal case and rigid leads. They are produced mainly from purified silicon. On the cathode side, a thread is made to fix it on the heat sink.
• Powerful (power) diodes operate in circuits with a current of more than 10 A. Their cases are made of cermet and metal glass. Constructive design - pin or tablet. Manufacturers offer models for currents up to 100,000 A and voltages up to 6 kV. They are mainly made of silicon.

Diode detectors

Such devices are obtained by combining diodes with capacitors in a circuit. They are designed to extract low frequencies from modulated signals. Present in most household appliances - radios and televisions. As radiation detectors, photodiodes are used that convert light falling on the photosensitive area into an electrical signal.

Limiting devices

Overload protection is provided by a chain of several diodes, which are connected to the supply buses in the opposite direction. When observing the standard operating mode, all diodes are closed. However, when the voltage exceeds the permissible designation, one of the protective elements is triggered.

Diode switches

Switches, which are a combination of diodes, are used to instantly change high frequency signals. Such a system is controlled by constant electric current. The high frequency and control signals are separated by capacitors and inductors.

Diode spark protection

Effective spark protection is achieved by combining a voltage limiting shunt diode barrier with current limiting resistors.

Parametric diodes

Used in parametric amplifiers, which are a subtype of resonant regenerative amplifiers. The principle of operation is based on a physical effect, which consists in the fact that when signals of different frequencies arrive at a nonlinear capacitance, part of the power of one signal can be directed to an increase in the power of another signal. The element designed to contain non-linear capacitance is a parametric diode.

Mixing diodes

Mixers are used to transform microwave signals into intermediate frequency signals. Signal transformation is carried out due to the nonlinearity of the mixing diode parameters. Devices with a Schottky barrier, varicaps, inverted diodes, Mott diodes are used as mixing microwave diodes.

Multiplier diodes

These microwave devices are used in frequency multipliers. They can operate in decimeter, centimeter, millimeter wavelength ranges. Typically, silicon and gallium arsenide devices are used as multiplying devices, often with the Schottky effect.

Tuning diodes

The principle of operation of tuning diodes is based on the dependence of the barrier capacitance of the pn junction on the magnitude of the reverse voltage. Silicon and gallium arsenide devices are used as tuning devices. These parts are used in frequency tuning devices in the super-frequency range.

Generator diodes

To generate signals in the microwave range, devices of two main types are in demand - avalanche-transit and Gunn diodes. Some generator diodes, provided that they are switched on in a certain mode, can perform the functions of multiplying devices.

Types of diodes by type of construction

Zener Diodes (Zener Diodes)

These devices are capable of maintaining performance in electrical breakdown mode. In low-voltage devices (voltage up to 5.7 V), tunnel breakdown is used, in high-voltage devices, avalanche breakdown. Stabilization of low voltages is provided by stabilizers.

Stabilizers

A stabilizer, or normalizer, is a semiconductor diode in which the forward branch of the current-voltage characteristic is used to stabilize the voltage (that is, in the forward bias region, the voltage across the stabilizer weakly depends on the current). A distinctive feature of stabilizers in comparison with zener diodes is a lower stabilization voltage (approximately 0.7-2 V).

Schottky diodes

Devices used as rectifying, multiplying, tuning devices operate on the basis of a metal-semiconductor contact. Structurally, they are low-resistance silicon wafers on which a high-resistance film with the same type of conductivity is applied. A metal layer is vacuum deposited on the film.

Varicaps

Varicaps function as a capacitor whose value changes with voltage. The main characteristic of this device is capacitance-voltage.

Tunnel diodes

These semiconductor diodes have a falling voltage-current characteristic due to the tunneling effect. A modification of the tunnel device is a reverse diode, in which the negative resistance branch is expressed little or absent. The reverse leg of a reversed diode corresponds to the forward leg of a conventional diode device.

Thyristors

Unlike a conventional diode, a thyristor, in addition to the anode and cathode, has a third control electrode. These models are characterized by two stable states - open and closed. According to the device, these parts are divided into dinistors, trinistors, triacs. Silicon is mainly used in the manufacture of these products.

Triacs

Triacs (symmetric thyristors) are a type of thyristor used for switching in AC circuits. Unlike a thyristor, which has a cathode and an anode, it is incorrect to call the main (power) terminals of the triac a cathode or anode, since, due to the structure of the triac, they are both at the same time. The triac remains open as long as the current flowing through the main terminals exceeds a certain amount, called the holding current.

Dinistors

A dynistor, or diode thyristor, is a device that does not contain control electrodes. Instead, they are controlled by the voltage applied between the main electrodes. Their main application is to control high-power loads using weak signals. Dinistors are also used in the manufacture of switching devices.

Diode bridges

These are 4, 6 or 12 diodes that are connected to each other. The number of diode elements is determined by the type of circuit, which can be single-phase, three-phase, full- or half-bridge. Bridges perform the function of rectifying current. Often used in automotive generators.

Photodiodes

Designed to convert light energy into an electrical signal. The principle of operation is similar to solar panels.

LEDs

These devices emit light when connected to electrical current. LEDs with a wide range of colors and power are used as indicators in various devices, light emitters in optocouplers, and are used in mobile phones to illuminate keyboards. High power devices are in demand as modern light sources in lanterns.

Infrared diodes

This is a type of LED that emits light in the infrared range. It is used in wireless communication lines, instrumentation, remote control devices, in video surveillance cameras for viewing the territory at night. Infrared emitting devices generate light in a range that is not visible to the human eye. It can be detected using a mobile phone camera.

Gunn diodes

This type of super-frequency diodes is made of a semiconductor material with a complex conduction band structure. Electronically conductive gallium arsenide is commonly used in the manufacture of these devices. This device does not have a p-n junction, that is, the characteristics of the device are intrinsic, and not arising at the junction of two different semiconductors.

Magnetodiodes

In such devices, the I – V characteristic changes under the influence of a magnetic field. The devices are used in contactless buttons intended for information input, motion sensors, control devices and measurement of non-electrical quantities.

Laser diodes

These devices, which have a complex crystal structure and a complex operating principle, provide a rare opportunity to generate a laser beam in a domestic environment. Due to their high optical power and wide functionality, the devices are effective in high-precision measuring devices for household, medical, and scientific applications.

Avalanche and avalanche-transit diodes

The principle of operation of the devices consists in the avalanche multiplication of charge carriers with a reverse bias of the p-n junction and their overcoming of the span for a certain time interval. Gallium arsenide or silicon are used as starting materials. The devices are mainly intended for obtaining ultra-high frequency oscillations.

PIN diodes

The PIN devices between the p and n regions have their own undoped semiconductor (i region). The wide unalloyed area prevents this device from being used as a rectifier. However, PIN diodes are widely used as mixing, detector, parametric, switching, limiting, tuning, and generator diodes.

Triodes

Triodes are vacuum tubes. It has three electrodes: a thermionic cathode (direct or indirect heating), an anode and a control grid. Today, triodes are almost completely replaced by semiconductor transistors. The exception is the areas where the conversion of signals with a frequency of the order of hundreds of MHz - GHz of high power with a small number of active components is required, and the dimensions and weight do not matter much.

Diode marking

The marking of semiconductor diode devices includes numbers and letters:

• The first letter characterizes the source material. For example, K is silicon, G is germanium, A is gallium arsenide, I is indium phosphide.
• The second letter is the class or group of the diode.
• The third element, usually numeric, denotes the application and electrical properties of the model.
• The fourth element is a letter (from A to Z), denoting a development option.

Example: KD202K - silicon rectifier diffusion diode.

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