Types of diodes and their application. Designation of different types of diodes in the diagram

- 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 - 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, due to the high resistance, is closed. The 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 is tube (electrovacuum) 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 goes into a closed position and the current practically does not pass.

Another type of non-semiconductor devices - gas-filled, of which only arc-discharge models are in use today. Gastrons (devices with hot cathodes) are filled with inert gases, mercury vapors or vapors of other metals. Special oxide anodes used in gas-filled diodes are able to withstand 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. P-type semiconductors are characterized by an excess of positive charges, n-type - an excess of negative charges (electrons). If semiconductors of these two types are nearby, then near the boundary separating them there are two narrow charged regions, which are called p-n junction. Such a device with two types of semiconductors with different impurity conductivity (or a semiconductor and a metal) and a p-n junction is called semiconductor diode. It is semiconductor diode devices that are most in demand in modern devices for various purposes. Many modifications of such devices have been developed for different fields of application.

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 wafer, in which there are two regions with different impurity conductivity. The most popular products are made of germanium and silicon. The advantages of such models are the ability to operate with 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 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, since they are mainly used to convert 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 devices.

Materials for the manufacture of diodes

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

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 the technical task, for example, in low-power and precision electrical circuits.

Types of diodes by frequency range

According to the operating frequency, diodes are divided into:

• Low-frequency - up to 1 kHz.
• High-frequency and ultra-high-frequency - up to 600 MHz. At such frequencies, point devices are mainly used. The junction capacitance should be low - no more than 1-2 pF. They are effective in a wide frequency range, 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.

Applications of diodes

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

Rectifier Diodes

These devices are used to rectify the sinusoid of alternating current. Their principle of operation is based on the property of the device to go into a closed state when reverse biased. As a result of the operation of the diode device, the negative half-waves of the current sinusoid are cut off. According to the power dissipation, which depends on the maximum allowed direct 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. The products are distinguished by their low weight and compact dimensions, since their case is made of polymeric materials.
• Medium Power Diodes can operate in the current range of 0.3-10.0 A. In most cases, they have a metal case and hard leads. They are produced mainly from purified silicon. On the cathode side, a thread is made for fixing on a 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. Design - pin or tablet. Manufacturers offer models designed for currents up to 100,000 A and voltages up to 6 kV. They are mainly made from 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. They are present in most household appliances - radios and televisions. As radiation detectors, photodiodes are used, which convert the light falling on the photosensitive area into an electrical signal.

Restrictive devices

Overload protection is provided by a chain of several diodes that are connected to the supply rails in the opposite direction. Under standard operating conditions, all diodes are closed. However, when the voltage exceeds the permissible value, one of the protective elements is activated.

Diode switches

Switches are combinations of diodes that are used to instantly change high frequency signals. Such a system is controlled by direct electric current. High-frequency and control signals are separated using capacitors and inductors.

Diode spark protection

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

Parametric diodes

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

Mixing Diodes

Mixing devices are used to transform microwave signals into intermediate frequency signals. The signal transformation is carried out due to the non-linearity of the parameters of the mixing diode. As mixing microwave diodes, devices with a Schottky barrier, varicaps, inverted diodes, and Mott diodes are used.

Multiplier Diodes

These microwave devices are used in frequency multipliers. They can operate in the decimeter, centimeter, millimeter wavelength ranges. As a rule, silicon and gallium arsenide devices are used as multipliers, 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 p-n 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 microwave 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, when turned on in a certain mode, can perform the functions of multiplier devices.

Types of diodes by design type

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 is used. Stabistors provide stabilization of low voltages.

Stabistors

A stabiistor, or normistor, is a semiconductor diode in which the direct branch of the current-voltage characteristic is used to stabilize the voltage (that is, in the forward bias region, the voltage across the stabistor is weakly dependent on current). A distinctive feature of stabistors compared to zener diodes is a lower stabilization voltage (about 0.7-2 V).

Schottky diodes

Devices used as rectifiers, multipliers, 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 deposited. A metal layer is deposited onto the film by vacuum.

Varicaps

Varicaps perform the functions of a capacitance, the value of which changes with a change in voltage. The main characteristic of this device is volt-farad.

tunnel diodes

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

Thyristors

Unlike a conventional diode, the 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 production 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) conclusions of a triac a cathode or an anode, since, due to the structure of a 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 dinistor, or diode thyristor, is a device that does not contain control electrodes. Instead, they are controlled by a voltage applied between the main electrodes. Their main application is to control a powerful load with weak signals. Dinistors are also used in the manufacture of switching devices.

diode bridges

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

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 an electrical current. LEDs, which have a wide color gamut of illumination and power, are used as indicators in various devices, light emitters in optocouplers, and are used in mobile phones to illuminate the keyboard. 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 cableless communication lines, instrumentation, remote control devices, in CCTV cameras to view 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 the camera of a mobile phone.

Gunn Diodes

This kind of microwave diodes is made of a semiconductor material with a complex structure of the conduction band. Typically, electronically conductive gallium arsenide is used in the manufacture of these devices. There is no p-n junction in this device, that is, the characteristics of the device are their own, and not arising at the interface between two different semiconductors.

Magnetic diodes

In such devices, the CVC changes under the influence of a magnetic field. The devices are used in contactless buttons for entering information, motion sensors, control devices and measurement of non-electrical quantities.

Laser diodes

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

Avalanche and avalanche-span diodes

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

PIN diodes

PIN devices between p- and n-regions have their own undoped semiconductor (i-region). The wide unalloyed area does not allow using this device 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 it is required to convert signals with a frequency of the order of hundreds of MHz - GHz of high power with a small number of active components, 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 alphabetic (from A to Z), denoting the development option.

Example: KD202K - silicon rectifier diffusion diode.

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Diode is a two-electrode semiconductor device. This is accordingly Anode(+) or positive electrode and Cathode(-) or negative electrode. It is customary to say that a diode has (p) and (n) regions, they are connected to the terminals of the diode. Together they form a p-n junction. Let's take a closer look at what this p-n junction is. A semiconductor diode is a purified silicon or germanium crystal, in which an acceptor impurity is introduced into the (p) region, and a donor impurity is introduced into the (n) region. Ions can act as a donor impurity. Arsenic, and as an acceptor impurity ions India. The main property of a diode is the ability to pass current in only one direction. Consider the figure below:

This figure shows that if the diode is turned on anode to the nutritional plus cathode to the minus of the supply, then the diode is in the open state and conducts current, since its resistance is negligible. If the diode is on anode to the minus, and cathode on the plus side, then the resistance of the diode will be very large, and there will be practically no current in the circuit, or rather it will be, but so small that it can be neglected.

You can find out more by looking at the following graph, the Volt-Amp characteristic of a diode:

In direct connection, as we can see from this graph, the diode has a small resistance, and accordingly passes current well, and in reverse connection, up to a certain voltage value, the diode is closed, has high resistance and practically does not conduct current. It is easy to verify this, if you have a diode and a multimeter at hand, you need to put the device in the sound continuity position, or by setting the multimeter switch opposite the diode icon, in extreme cases, you can try to ring the diode by setting the switch to position 2 KΩ resistance measurement. The diode is depicted on the schematic diagrams as in the figure below, remember where which conclusion is easy: the current, as you know, always flows from plus to minus, and so the triangle in the image of the diode, as it were, shows the direction of the current with its apex, that is, from plus to minus.

By connecting the red probe of the multimeter to the Anode, we can make sure that the diode passes current in the forward direction, on the device screen there will be numbers equal to ~ 800-900 or close to it. By connecting the probes the other way around, the black probe to the anode, the red probe to the cathode, we will see a unit on the screen, which confirms that the diode does not pass current in the reverse connection. The diodes discussed above are planar and point. Planar diodes are designed for medium and high power and are used mainly in rectifiers. Point diodes are designed for low power and are used in radio detectors, they can operate at high frequencies.

Planar and point diode

What are the types of diodes?

A) The photo shows the diode we discussed above.

b) This picture shows zener diode, (foreign name Zener diode), it is used when turning the diode back on. The main goal is to keep the voltage stable.

Dual-anode zener diode - image on the diagram

IN) double sided(or two-anode) zener diode. The advantage of this zener diode is that it can be turned on regardless of polarity.

D), can be used as an amplifying element.

E), used in high-frequency circuits for detection.

E), used as a variable capacitor.

G), when the device is illuminated in the circuit connected to it, a current arises due to the appearance of pairs of electrons and holes.

H), well-known, and probably the most widely used devices, after conventional rectifier diodes. They are used in many electronic devices for indication and not only.

Rectifier Diodes are also produced in the form of diode bridges, let's analyze what it is - these are four diodes connected to obtain a constant (rectified) current in one housing. They are connected by bridge circuit, standard for rectifiers:

They have four marked outputs: two for connecting alternating current, and plus and minus. The photo shows a diode bridge KC405:

Now let's take a closer look at the scope of LEDs. Light-emitting diodes (or rather, an LED lamp) are also produced by the industry for indoor lighting, as an economical and durable light source, with a base that allows them to be screwed into a conventional incandescent lamp holder.

LED lamp photo

LEDs exist in different packages, including SMD.

The so-called RGB LEDs are also produced, inside them there are three crystals of LEDs with a different glow of Red-Green-Blue, respectively Red - Green - Blue, these LEDs have four outputs and allow any color to be visible by mixing colors.

These SMD LEDs are often available as strips with pre-installed resistors and allow you to connect them directly to a 12 volt power supply. You can use a special controller to create lighting effects:

rgb controller

When used, they do not like it when they are supplied with a supply voltage higher than that for which they are designed and can burn out immediately or after some time, so the voltage of the power source must be calculated using the formulas. For Soviet LEDs of the AL-307 type, the supply voltage should be approximately 2 volts, for imported 2-2.5 volts, naturally with current limitation. To power LED strips, if a special controller is not used, a stabilized power supply is required. Material prepared - AKV.

Discuss the article DIODES

What is a diode? This is an element that has received different conductivity. It depends on how the electric current flows. The application of the device depends on the circuit that needs to limit the following of this element. In this article we will talk about the device of the diode, as well as what types exist. Consider the scheme and where these elements are applied.

History of appearance

It so happened that two scientists began to work on the creation of diodes at once: a British and a German. It should be noted that their discoveries were slightly different. The first based the invention on tube triodes, and the second on solid state ones.

Unfortunately, at that time science was not able to make a breakthrough in this area, but a lot of reasons were given for reflection.

A few years later, diodes were again discovered (formally). Thomas Edison patented this invention. Unfortunately, in all his works during his lifetime, this was not useful to him. Therefore, similar technology was developed by other scientists in different years. Until the beginning of the 20th century, these inventions were called rectifiers. And only after a while William Eckles used two words: di and odos. The first word translates as two, and the second - the way. The language in which the name was given is Greek. And if you translate the expression in full, then "diode" means "two ways".

The principle of operation and basic information about diodes

The diode in its structure has electrodes. We are talking about the anode and cathode. If the first has a positive potential, then the diode is called open. Thus, the resistance becomes small and the current passes. If the potential is positive at the cathode, then the diode is not open. It does not pass electric current and has a high resistance index.

How a diode works

In principle, what is a diode, we figured it out. Now we need to understand how it works.

The case is often made of glass, metal or ceramics. Most often, certain compounds are used instead of the latter. Under the body you can see two electrodes. The simplest will have a thread of small diameter.

Inside the cathode is a wire. It is considered a heater, as it has heating in its functions, which takes place according to the laws of physics. The diode heats up due to the work of electric current.

Silicon or germanium is also used in the manufacture. One side of the device has a shortage of electrodes, the other side has an excess of them. Due to this, special boundaries are created, which are provided by the transition of the p-n type. Thanks to him, the current is conducted in the direction in which it is necessary.

Characteristics of diodes

The diode in the diagram is already shown, now you should find out what you need to pay attention to when buying a device.

As a rule, buyers are guided by only two nuances. We are talking about the maximum current strength, as well as the reverse voltage at maximum rates.

The use of diodes in everyday life

Quite often, diodes are used in automotive generators. Which diode to choose, you should decide for yourself. It should be noted that the machines use complexes of several devices, which are recognized as a diode bridge. Often, such devices are built into televisions and receivers. If you use them together with capacitors, you can achieve separation of frequencies and signals.

In order to protect the consumer from electric current, a complex of diodes is often built into the devices. Such a system of protection is considered quite effective. It must also be said that the power supply most often uses such a device for any devices. Thus, LED diodes are now quite common.

Types of diodes

Having considered what a diode is, it is necessary to emphasize what types exist. As a rule, devices are divided into two groups. The first is considered semiconductor, and the second is not semiconductor.

At the moment, the first group is popular. The name is associated with the materials from which such a device is made: either from two semiconductors, or from ordinary metal with a semiconductor.

At the moment, a number of special types of diodes have been developed, which are used in unique circuits and devices.

Zener diode, or zener diode

This type is used in voltage stabilization. The fact is that such a diode, when a breakdown occurs, sharply increases the current, while the accuracy is as high as possible. Accordingly, the performance of this type of diode is quite surprising.

tunnel

If we explain in simple terms what kind of diode it is, then it should be said that this type creates a negative type of resistance in the current-voltage characteristics. Often such a device is used in generators and amplifiers.

reversed diode

If we talk about this type of diodes, then this device can change the voltage to the minimum side, operating in open mode. This device is an analogue of a tunnel type diode. Although it works on a slightly different basis, it is based precisely on the effect described above.

Varicap

This device is a semiconductor device. It is characterized in that it has an increased capacity that can be controlled. It depends on the reverse voltage. Often, such a diode is used when setting up and calibrating oscillatory-type circuits.

Light-emitting diode

This type of diode emits light, but only if the current flows in the forward direction. Most often, it is this device that is used wherever lighting should be created with minimal energy consumption.

Photodiode

This device has completely the opposite characteristics, if we talk about the previous described option. Thus, it generates charges only if light hits it.

Marking

It should be noted that a feature of all devices is that each of the elements has a special designation. Thanks to them, you can find out the characteristic of the diode, if it belongs to the semiconductor type. The body consists of four components. Now let's look at the markings.

In the first place there will always be a letter or number that indicates the material from which the diode is made. Thus, the parameters of the diode will be easy to find out. If the letter G, K, A or I is indicated, then this means germanium, silicon, gallium arsenide and indium. Sometimes instead of them, numbers from 1 to 4, respectively, can be indicated.

The second place will be the type. It also has different meanings and its own characteristics. There can be rectifier units (C), varicaps (B), tunnel (I) and zener diodes (C), rectifiers (D), microwave (A).

The penultimate place is occupied by a number that will indicate the area in which the diode is used.

The fourth place will be set to a number from 01 to 99. It will indicate the development number. In addition, the manufacturer can apply various designations to the case. However, as a rule, they are used only on devices created for certain circuits.

For convenience, diodes can be marked with graphic images. We are talking about dots, stripes. There is no logic in these figures. Therefore, in order to understand what the manufacturer had in mind, you will have to read the instructions.

triodes

This type of electrode is analogous to a diode. What is a triode? It is a bit similar in its complex to the devices described above, but it has other functions and design. The main difference between a diode and a triode would be that it has three terminals and is most commonly referred to as a transistor itself.

The principle of operation is calculated on the fact that, using a small signal, current will be output to the circuit. Diodes and transistors are used in almost every device that has an electronic type. It is also about processors.

Advantages and disadvantages

A laser diode, like any other, has advantages and disadvantages. In order to emphasize the advantages of these devices, it is necessary to specify them. In addition, we will make a small list of cons.

Of the advantages, it should be noted the low cost of diodes, an excellent service life, a high rate of operation, you can still use these devices when working with alternating current. It should also be noted the small size, which allows you to place devices on any scheme.

As for the minuses, it should be highlighted that there are currently no semiconductor-type devices that can be used in high voltage devices. That is why you have to embed the old counterparts. It should also be noted that high temperatures are very detrimental to diodes. It shortens the service life.

The first copies had very little accuracy. That is why the characteristics of the devices were rather poor. Diode lamps had to be unpacked. What does this mean? Some devices could receive completely different properties, even made in the same batch. After screening out unusable devices, the elements were labeled, which described their real characteristics.

All diodes that are made of glass have received a feature: they are sensitive to light. Thus, if the device can open, that is, has a cover, then the whole circuit will work completely differently, depending on whether the space for light is open or closed.

Diodes belong to the category of electronic devices that work on the principle of a semiconductor, which reacts in a special way to the voltage applied to it. The appearance and circuit designation of this semiconductor product can be found in the figure below.

A feature of the inclusion of this element in the electronic circuit is the need to observe the polarity of the diode.

Additional explanation. By polarity is meant a strictly established switching order, which takes into account where is the plus and where is the minus of this product.

These two symbols are tied to its terminals, called the anode and cathode, respectively.

Features of functioning

It is known that any semiconductor diode, when a constant or alternating voltage is applied to it, passes current in only one direction. If it is turned on again, direct current does not flow, since the n-p junction will be biased in a non-conductive direction. It can be seen from the figure that the minus of the semiconductor is located on the side of its cathode, and the plus is on the opposite end.

Especially clearly the effect of one-way conduction can be confirmed by the example of semiconductor products, called light-emitting diodes, which work only if they are turned on correctly.

In practice, situations are not uncommon when there are no obvious signs on the body of the product that allow you to immediately tell where it has which pole. That is why it is important to know the special signs by which you can learn to distinguish between them.

Methods for determining polarity

To determine the polarity of a diode product, you can use various methods, each of which is suitable for certain situations and will be considered separately. These methods are conditionally divided into the following groups:

• A visual inspection method that allows you to determine the polarity according to the existing markings or characteristic features;
• Checking with a multimeter included in the dialing mode;
• Finding out where is plus and where is minus by assembling a simple circuit with a miniature light bulb.

Let's consider each of these approaches separately.

visual inspection

This method allows you to decipher the polarity according to the special marks on the semiconductor product. For some diodes, this may be a dot or an annular strip shifted towards the anode. Some samples of the old brand (KD226, for example) have a characteristic pointed shape on one side, which corresponds to the plus. On the other, completely flat end, respectively, there is a minus.

Note! When visually inspecting LEDs, for example, it is found that one of their legs has a characteristic protrusion.

On this basis, it is usually determined where such a diode has a plus, and where is the opposite contact.

Application of the measuring device

The easiest and most reliable way to determine the polarity is to use a measuring device such as a "multimeter", included in the "Continuity" mode. When measuring, you should always remember that a plus is supplied to the cord in red insulation from the built-in battery, and minus to the cord in black insulation.

After arbitrarily connecting these "ends" to the terminals of a diode with unknown polarity, you need to follow the readings on the display of the device. If the indicator shows a voltage of the order of 0.5-0.7 Volts, this means that it is turned on in the forward direction, and the leg to which the probe in red insulation is connected is positive.

If the indicator shows “one” (infinity), we can say that the diode is turned on in the opposite direction, and based on this it will be possible to judge its polarity.

Additional Information. Some radio amateurs use a socket designed to measure transistor parameters to test LEDs.

The diode in this case is turned on as one of the transitions of the transistor device, and its polarity is determined by whether it glows or not.

Inclusion in the scheme

In an extreme case, when it is not possible to visually determine the location of the pins, and there is no measuring device at hand, you can use the method of including a diode in a simple circuit shown in the figure below.

When it is included in such a circuit, the light bulb will either light up (this means that the semiconductor passes current through itself) or not. In the first case, the battery plus will be connected to the positive output of the product (anode), and in the second case, on the contrary, to its cathode.

In conclusion, we note that there are quite a few ways to determine the polarity of a diode. At the same time, the choice of a specific method for its detection depends on the conditions of the experiment and the capabilities of the user.

Video

In mechanics, there are devices that allow air or liquid to pass in only one direction.Remember how you pumped up the wheel of a bicycle or car. Why didn't air come out of the wheel when you removed the pump hose? Because on the camera, in the pipe where you insert the pump hose, there is such an interesting little thing -. Here it just lets air through only in one direction, and blocks its passage in the other direction.

Electronics - this is the same hydraulics or pneumatics. But the whole joke is that in electronics, instead of liquid or air, electric current is used. To draw an analogy: a water tank is a charged capacitor, a hose is a wire, an inductor is a wheel with blades

which can not be immediately dispersed, and then it is impossible to abruptly stop.

Then what is a nipple in electronics? And we will call a nipple a radio element -. And in this article we will get to know him better.

A semiconductor diode is an element that allows current to flow in one direction and blocks it in the other direction. This is a kind of nipple ;-).

Some diodes look almost exactly like resistors:

And some look a little different:

There is also an SMD version of the diodes:

Diode has two terminals, like a resistor, but these pins, unlike a resistor, have specific names - anode and cathode(and not plus and minus, as some illiterate electronic engineers say). But how can we determine what is what? There are two ways:

1) on some diodes the cathode is indicated by a stripe different from body color

2) can test diode with multimeter and find out where his cathode is, and where is the anode. At the same time, check its performance. This method is iron ;-). How to test a diode with a multimeter can be found in this article.

If we apply a plus to the anode, and a minus to the cathode, then our diode will “open” and the electric current will flow calmly through it. And if a minus is applied to the anode, and a plus to the cathode, then the current through the diode will not flow. A kind of nipple ;-). In the diagrams, a simple diode is denoted as follows:

Where is the anode and where is the cathode is very easy to remember if you remember the funnel for pouring liquids into the narrow necks of bottles. A funnel is very similar to a diode circuit. We pour it into the funnel, and the liquid runs very well with us, and if you turn it over, then try to pour it through the narrow neck of the funnel ;-).

Diode characteristics

Let's look at the characteristics of the KD411AM diode. We are looking for its characteristics on the Internet, driving into the search “datasheet KD411AM”

To explain the parameters of a diode, we will also need its

1) Reverse maximum voltage U arr - this is the voltage of the diode, which it can withstand when connected in the opposite direction, while current will flow through it I arr is the current strength when the diode is connected in reverse. When the reverse voltage is exceeded in the diode, the so-called avalanche breakdown occurs, as a result of which the current increases sharply, which can lead to complete thermal destruction of the diode. In our diode under study, this voltage is 700 volts.

2) Maximum forward current I pr is the maximum current that can flow through the diode in the forward direction. In our case, this is 2 amperes.

3) Maximum frequency F d , which must not be exceeded. In our case, the maximum diode frequency will be 30 kHz. If the frequency is higher, then our diode will not work correctly.

Types of diodes

zener diodes

They are the same diodes. Even from the name it is clear that zener diodes stabilize something. A they stabilize the voltage. But in order for the zener diode to perform stabilization, one condition is required.They should be connected opposite to the diodes. The anode is negative and the cathode is positive. Strange isn't it? But why is that? Let's figure it out. In the Volt-ampere characteristic (CVC) of the diode, the positive branch is used - the forward direction, but in the zener diode the other part of the CVC branch is the reverse direction.

Below on the graph we see a 5 volt zener diode. No matter how much the current strength changes, we will still get 5 Volts ;-). Cool, isn't it? But there are also pitfalls. The current strength should not be more than in the description for the diode, otherwise it will fail from high temperature - Joule-Lenz Law. The main parameter of the zener diode is stabilization voltage(Ust). Measured in Volts. On the graph you see a zener diode with a stabilization voltage of 5 volts. There is also a range of current strength at which the zener diode will work - is the minimum and maximum current(I min , I max). Measured in amperes.

Zener diodes look exactly the same as ordinary diodes:

The diagrams are marked like this:

LEDs

LEDs- a special class of diodes that emit visible and invisible light. Invisible light is light in the infrared or ultraviolet range. But for industry, LEDs with visible light still play a big role. They are used for indication, design of signboards, luminous banners, buildings and also for lighting. LEDs have the same parameters as any other diodes, but usually their maximum current is much lower.

Limit reverse voltage (U arr) can reach 10 volts. Maximum current ( Imax) will be limited to about 50 mA for simple LEDs. For lighting more. Therefore, when connecting a conventional diode, you need to connect a resistor in series with it. The resistor can be calculated using a simple formula, but ideally it is better to use a variable resistor, select the desired glow, measure the value of the variable resistor and put a constant resistor with the same value there.

Lighting lamps made of LEDs consume a penny of electricity and are cheap.

LED strips, consisting of many LEDs, are in great demand. They look very beautiful.

In the diagrams, the LEDs are indicated as follows:

Do not forget that LEDs are divided into indicator and lighting. Indicator LEDs have a weak glow and are used to indicate any processes occurring in the electronic circuit. They are characterized by a weak glow and low current consumption.

Well, lighting LEDs are those that are used in your Chinese lanterns, as well as in LED lamps.

The LED is a current device, that is, for its normal operation, it requires a rated current, not a voltage. At the rated current, some falls on the LED, which depends on the type of LED (rated power, color, temperature). Below is a table showing what voltage drop occurs on LEDs of different glow colors at rated current:

How to check the LED can be found in this article.

Thyristors

Thyristors are diodes, the conductivity of which is controlled using the third output - the control electrode (UE). The main application of thyristors is the control of a powerful load using a weak signal applied to the control electrode.Thyristors look like diodes or transistors. Thyristors have so many parameters that there is not enough article to describe them.The main parameter is I os, cf.- the average value of the current that should flow through the thyristor in the forward direction without harm to its health.An important parameter is the opening voltage of the thyristor - ( u u), which is fed to the control electrode and at which the thyristor is fully opened.

and this is how power thyristors look like, that is, thyristors that work with high current:

In the diagrams, triode thyristors look like this:

There are also types of thyristors - dinistors and triacs. Dinistors do not have a control electrode and it looks like a regular diode. Dinistors begin to pass an electric current through themselves in direct connection when the voltage on it exceeds a certain value.Triacs are the same triode thyristors, but when turned on, they pass electric current through themselves in two directions, so they are used in alternating current circuits.

Diode bridge and diode assemblies

Manufacturers also push several diodes into one case and connect them together in a certain sequence. Thus we get diode assemblies. Diode bridges are one of the varieties of diode assemblies.

On the diagrams diode bridge is marked like this:

There are also other types of diodes, such as varicaps, Gunn diode, Schottky diode, etc. In order to describe them all, we do not have enough eternity.