What is a diode? This is an element that has received different conductivity. It depends on how exactly the electric current flows. The use of the device depends on the circuit that needs to restrict the following of this element. In this article we will talk about the design of the diode, as well as what types exist. Let's look at the diagram and where these elements are used.

History of appearance

It so happened that two scientists began working on the creation of diodes: a Briton and a German. It should be noted that their findings 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 there were a lot of reasons for reflection.

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

Operating principle and basic information about diodes

The diode has electrodes in its structure. We are talking about the anode and cathode. If the first one has a positive potential, then the diode is called open. Thus, the resistance becomes small and current flows. If the potential is positive at the cathode, then the diode is not opened. He doesn't miss electricity and has a high resistance value.

How does a diode work?

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

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

There is a wire inside the cathode. It is considered a heater, since its functions include heating, which occurs according to the laws of physics. The diode heats up due to the operation of electric current.

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

Diode characteristics

The diode is already shown in the diagram, 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 maximum current, as well as reverse voltage at maximum levels.

Using diodes in everyday life

Quite often, diodes are used in automobile generators. You should decide for yourself which diode to choose. 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 the isolation of frequencies and signals.

In order to protect the consumer from electric current, a complex of diodes is often built into devices. This protection system is considered quite effective. It also needs to be said that the power supply most often for any devices uses such a device. 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 non-semiconductor.

On this 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 an ordinary metal with a semiconductor.

At the moment, a number of special types of diodes have been developed that 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 characteristics of this type of diode are quite amazing.

Tunnel

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

Reversed diode

If speak about this type 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 in a slightly different way, it is based precisely on the effect described above.

Varicap

This device is a semiconductor. It is characterized by having increased capacity, which can be controlled. This depends on the reverse voltage indicators. 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, this device is used wherever lighting needs to be created with minimum costs electricity.

Photodiode

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

Marking

It should be noted that a feature of all devices is that each element has a special designation. Thanks to them, you can find out the characteristics of the diode if it is of the semiconductor type. The body consists of four components. Now we should consider 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 numbers from 1 to 4 may be indicated instead, respectively.

The second place will indicate the type. It also has different meanings and its own characteristics. There may be rectifier units (C), varicaps (V), tunnel diodes (I) and zener diodes (C), rectifiers (D), microwaves (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 markings to the body. However, as a rule, they are used only on devices created for specific circuits.

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

Triodes

This type of electrode is an analogue of a diode. What is a triode? It is somewhat similar in complex to the devices described above, but has different functions and design. The main difference between a diode and a triode will be that it has three terminals and is most often referred to as a transistor itself.

The operating principle is designed to output current into the circuit using a small signal. Diodes and transistors are used in almost every device that has electronic type. We are also talking 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 disadvantages.

The advantages include the low cost of diodes, excellent service life, high service life, and you can also use these devices when working with alternating current. It should also be noted that the devices are small in size, allowing them to be placed on any circuit.

As for the disadvantages, it should be emphasized that at the moment there are no semiconductor-type devices that can be used in devices with high voltage. That is why you will have to build in old analogues. It should also be noted that diodes have a very detrimental effect heat. It shortens the service life.

The first copies had very little accuracy. This is why the performance of the devices was quite poor. The LED lamps had to be unpacked. What does this mean? Some devices could receive completely different properties, even manufactured in the same batch. After screening out unsuitable devices, the elements were marked, which described their real characteristics.

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

We all know very well what a semiconductor diode is, but few of us know about the principle of operation of a diode. Today, especially for beginners, I will explain the principle of its operation. As is known, a diode passes current well on one side, but very poorly on the opposite direction. The diode has two terminals - anode and cathode. Not a single electronic device can do without the use of diodes. The diode is used to rectify alternating current, using a diode bridge which consists of four diodes, you can turn alternating current into constant, or using six diodes to turn three-phase voltage into single-phase, diodes are used in a variety of power supplies, in audio-video devices, almost everywhere. Here you can see photos of some.

You can notice a drop in the diode output entry level voltage by 0.5-0.7 volts. For lower voltage power supply devices, a Schottky diode is used; on such a diode the smallest voltage drop is observed - about 0.1V. Schottky diodes are mainly used in radio transmitting and receiving devices and in other devices operating mainly at high frequencies. The operating principle of a diode is quite simple at first glance: a diode is a semiconductor device with one-way conductivity of electric current.

The diode terminal connected to the positive pole of the power source is called the anode, and the negative terminal is called the cathode. The diode crystal is mainly made of germanium or silicon, one region of which has n-type electrical conductivity, that is, a hole region, which contains an artificially created lack of electrons, the other - n-type conductivity, that is, contains an excess of electrons, the boundary between them is called a n-n junction , n is the first letter of the word positive in Latin, n is the first letter of the word negative. If a positive voltage is applied to the anode of the diode, and a negative voltage is applied to the cathode, then the diode will pass current, this is called direct connection, in this position the diode is open, if reverse is applied, the diode will not pass current, in this position the diode is closed, this is called reverse connection .

The reverse resistance of the diode is very high and in circuits it is considered a dielectric (insulator). You can assemble a semiconductor diode to demonstrate how it works simple diagram which consists of a power source, a load (for example, an incandescent lamp or a low-power electric motor) and the semiconductor diode itself. We connect all the components of the circuit in series, we supply plus from the power source to the anode of the diode, in series to the diode, that is, we connect one end of the light bulb to the cathode of the diode, and connect the other end of the same lamp to the minus of the power source. We observe the glow of the lamp, now we turn the diode over, the lamp will no longer glow because the diode is connected back, the transition is closed. I hope this will help you in some way in the future, newbies - A. Kasyan (AKA).

At the very beginning of radio engineering, the first active element was electric lamp. But already in the twenties of the last century, the first devices available for repetition by radio amateurs appeared and became very popular. These are detector receivers. Moreover, they were produced on an industrial scale, were inexpensive and provided reception for two or three domestic radio stations operating in the medium and long wave bands.

It was in detector receivers that the simplest semiconductor device was first used, initially called a detector and only later receiving its modern name - a diode.

A diode is a device consisting of only two layers of semiconductor. This is layer “p” - positive and layer “n” - negative. At the boundary of two semiconductor layers, “ p-n” transition. The anode is the “p” region, and the cathode is the “n” region. Any diode is capable of conducting current only from the anode to the cathode. On the schematic diagrams it is designated as follows.

How does a semiconductor diode work?

In an “n” type semiconductor there are free electrons, particles with a minus sign, and in a “p” type semiconductor there are ions with a positive charge, they are usually called “holes”. Let's connect the diode to the power source in reverse connection, that is, we will apply a minus to the anode and a plus to the cathode. Attraction occurs between charges of different polarities and positively charged ions are drawn to the minus, and negative electrons drift to the plus of the power source. In a “p-n” junction there are no charge carriers and there is no movement of electrons. No movement of electrons - no electric current. The diode is closed.

When the diode is turned on directly, the reverse process occurs. As a result of the repulsion of unipolar charges, all carriers are grouped in the transition zone between two semiconductor structures. An electric transition field and recombination of electrons and holes arise between the particles. Electric current begins to flow through the p-n junction. The process itself is called “electron-hole conduction.” In this case, the diode is open.

A completely natural question arises: how can structures with different properties be obtained from one semiconductor material, that is, an “n” type semiconductor and a “p” type semiconductor. This can be achieved using an electrochemical process called doping, that is, introducing impurities of other metals into the semiconductor, which provide the desired type of conductivity. There are mainly three semiconductors used in electronics. This germanium (Ge), silicon (Si) And gallium arsenide (GaAs). Silicon, of course, is most widespread, since its reserves in the earth's crust are truly enormous, so the cost of silicon-based semiconductor devices is very low.

When adding a negligible amount of arsenic to the silicon melt ( As) we get a semiconductor “ n” type, and doping silicon with the rare earth element indium ( In), we get a semiconductor “ p” type. There are a lot of additives for doping semiconductor materials. For example, the introduction of gold atoms into the structure of a semiconductor increases the performance of diodes, transistors and integrated circuits, and the addition of a small number of various impurities into a gallium arsenide crystal determines the color of the LED.

Types of diodes and their scope.

The family of semiconductor diodes is very large. Outwardly, they are very similar, with the exception of some groups that differ structurally and in a number of parameters. The most common modifications of semiconductor diodes are:

It is also worth noting that each type of diode has subgroups. For example, among rectifiers there are also ultra-fast diodes. May be called as Ultra-Fast Rectifier , HyperFast Rectifier and so on. Example - Ultrafast Low Dropout Diode STTH6003TV/CW(analogue VS-60CPH03). This is a highly specialized diode, which is used, for example, in inverter-type welding machines. Schottky diodes are fast, but cannot withstand high reverse voltages, so ultra-fast rectifier diodes are used instead, which can withstand high reverse voltages and huge forward currents. Moreover, their performance is comparable to that of Schottky diodes.

Parameters of semiconductor diodes.

Semiconductor diodes have quite a lot of parameters and they are determined by the function that they perform in specific device. For example, in diodes that generate microwave oscillations, a very important parameter is the operating frequency, as well as the cutoff frequency at which the generation fails. But for rectifier diodes this parameter is completely unimportant.

In switching and switching diodes, the switching speed and recovery time, that is, the speed of full opening and full closing, are important. In high-power power diodes, power dissipation is important. To do this, they are mounted on special radiators. But diodes operating in low-current devices do not need any radiators.

But there are parameters that are considered important for all types of diodes, we list them:

U ave. – permissible voltage on the diode when current flows through it in the forward direction. You should not exceed this voltage, as this will lead to its damage.

U arr. – permissible voltage on the diode in the closed state. It is also called breakdown voltage. In the closed state, when no current flows through the p-n junction, a reverse voltage is formed at the terminals. If it exceeds the permissible value, this will lead to a physical “breakdown” of the pn junction. As a result, the diode will turn into an ordinary conductor (burn out).

Schottky diodes are very sensitive to excess reverse voltage, which very often fail for this reason. Conventional diodes, for example, silicon rectifiers, are more resistant to excess reverse voltage. When it is slightly exceeded, they switch to the mode reversible breakdown. If the diode crystal does not have time to overheat due to excessive heat generation, then the product can work for a long time.

I ave. – forward current of the diode. This is very important parameter, which should be taken into account when replacing diodes with analogues or when designing homemade devices. The magnitude of the forward current for different modifications can reach tens and hundreds of amperes. Particularly powerful diodes are installed on the radiator to remove heat, which is formed due to the thermal effect of the current. P-N junction when connected directly, it also has low resistance. At small operating currents its effect is not noticeable, but at currents of a few to tens of amperes the diode crystal heats up noticeably. For example, a rectifier diode bridge in an inverter welding machine must be installed on a radiator.

I arr. – diode reverse current. The reverse current is the so-called minority carrier current. It is formed when the diode is closed. The amount of reverse current is very small and in the vast majority of cases it is not taken into account.

U stable – stabilization voltage (for zener diodes). Read more about this parameter in the article about zener diode.

In addition, it should be borne in mind that all these parameters in the technical literature are printed with the “ max" The maximum permissible value is indicated here this parameter. Therefore, when choosing the type of diode for your design, you must count on the maximum permissible values.

Content:

The standard design of a semiconductor diode is made in the form semiconductor device. It has two terminals and one rectifying electrical junction. The device uses various properties associated with electrical transitions. The entire system is connected in a single housing made of plastic, glass, metal or ceramic. The part of the crystal with a higher concentration of impurities is called the emitter, and the area with a lower concentration is called the base. Diode markings and designation schemes are used in accordance with their individual properties, design features and technical characteristics.

Characteristics and parameters of diodes

Depending on the material used, diodes can be made of silicon or germanium. In addition, indium phosphide and gallium arsenide are used for their production. Germanium diodes have a higher transmission coefficient compared to silicon products. They have high conductivity at relatively low voltage. Therefore, they are widely used in the production of transistor receivers.

In accordance with technological characteristics and designs, diodes are distinguished as planar or point, pulse, universal or rectifier. Among them, a separate group should be noted, which includes, and. All of these signs make it possible to identify a diode by appearance.

The characteristics of diodes are determined by such parameters as forward and reverse currents and voltages, temperature ranges, maximum reverse voltage and other values. Depending on this, appropriate markings are applied.

Designations and color coding of diodes

Modern diode designations comply with new standards. They are divided into groups depending on the limiting frequency at which current transmission is enhanced. Therefore, diodes come in low, medium, high and ultra-high frequencies. In addition, they have different power dissipation: low, medium and high.

Diode marking is a short symbol of the element in a graphic design, taking into account the parameters and technical features conductor. The material from which the semiconductor is made is designated on the case with the corresponding letter symbols. These designations are affixed along with the purpose, type, electrical properties of the device and its symbol. This helps in the future to correctly connect the diode to electronic circuit devices.

The anode and cathode terminals are indicated by an arrow or plus or minus signs. Color codes and markings in the form of dots or stripes are applied near the anode. All designations and color coding allow you to quickly determine the type of device and use it correctly in various circuits. A detailed explanation of this symbolism is given in reference tables, which are widely used by specialists in the field of electronics.

Marking of imported diodes

Currently, foreign-made diodes are widely used. The design of the elements is made in the form of a board, on the surface of which a chip is fixed. The dimensions of the product are too small to allow marking to be applied to it. On larger elements, designations are present in full or abbreviated versions.

In electronics, SMD diodes make up about 80% of all products of this type used. Such a variety of details makes you pay more attention to the designations. Sometimes they may not coincide with the declared technical characteristics, so it is advisable to additional check questionable elements if they are planned for use in complex and precise circuits. It should be borne in mind that the markings of diodes of this type may be different on completely identical cases. Sometimes there are only alphabetic symbols, without any numbers. In this regard, it is recommended to use tables with diode sizes from different manufacturers.

For SMD diodes, the SOD123 package type is most often used. A colored stripe or embossing may be applied to one of the ends, which indicates a cathode with negative polarity to open the pn junction. The only inscription corresponds to the designation of the body.

The type of housing does not play a decisive role when using a diode. One of the main characteristics is the dissipation of some amount of heat from the surface of the element. In addition, the values ​​of the operating and reverse voltages, the maximum permissible current through the pn junction, power dissipation and other parameters are taken into account. All this data is indicated in reference books, and marking only speeds up the search for the desired element.

It is not always possible to determine the manufacturer by the appearance of the case. To find the desired product, there are special search engines in which you need to enter numbers and letters in a certain sequence. In some cases, diode assemblies do not carry any information at all, so in such cases only a reference book can help. Such simplifications, which make the diode designation very short, are explained by the extremely limited space for marking. When using screen or laser printing, it is possible to fit 8 characters per 4 mm2.

It is also worth considering the fact that the same alphanumeric code can denote completely different elements. In such cases, the entire electrical circuit is analyzed.

Sometimes the labeling indicates the release date and batch number. Such marks are applied to be able to track more modern modifications of products. The corresponding corrective documentation with number and date is issued. This allows you to more accurately determine specifications elements when assembling the most critical circuits. By using old parts for new drawings, you may not get the expected result; in most cases, the finished product simply refuses to work.

Diode marking anode cathode

Each diode, like a resistor, is equipped with two terminals - anode and cathode. These names should not be confused with plus and minus, which mean completely different parameters.

However, it is very often necessary to determine the exact match of each diode terminal. There are two ways to determine the anode and cathode:

• The cathode is marked with a stripe, which is noticeably different from the overall color of the body.
• The second option involves checking the diode with a multimeter. As a result, not only the location of the anode and cathode is established, but also the performance of the entire element is checked.