FROM What does practical electronics begin with? Of course with radio components! Their diversity is simply amazing. Here you will find articles about all kinds of radio components, get acquainted with their purpose, parameters and properties. Find out where and in what devices certain electronic components are used.

To go to the article of interest, click on the link or thumbnail image located next to brief description material.

How to buy radio components online? This question is asked by many radio amateurs. The article tells about how you can order radio components in the online store of radio components with delivery by mail.

In this article I will talk about how to buy radio components and electronic modules in one of the largest online stores AliExpress.com for very little money :)

In addition to the widespread flat SMD resistors, MELF resistors in a cylindrical housing are used in electronics. What are their advantages and disadvantages? Where are they used and how to determine their power?

The sizes of SMD resistors are standardized, and they are probably known to many. But is it really that simple? Here you will learn about two systems for coding the sizes of SMD components, learn how to determine the real size of a chip resistor by its size and vice versa. Meet the smallest representatives of SMD resistors that currently exist. In addition, a table of sizes of SMD resistors and their assemblies is presented.

Here you will learn what the temperature coefficient of resistance of a resistor (TCR) is, as well as what TCR different types of fixed resistors have. The formula for calculating TCR is given, as well as explanations about foreign designations like T.C.R and ppm / 0 С.

In addition to fixed resistors, variable and trimming resistors are actively used in electronics. About how the variables and trimmers are arranged, about their varieties, and will be discussed in the proposed article. The material is supported by a large number of photographs of various resistors, which will certainly appeal to novice radio amateurs who will be able to more easily navigate in all the variety of these elements.

Like any radio component, variables and trimmers have basic parameters. It turns out that there are not so few of them, and it will not hurt beginner radio amateurs to get acquainted with such interesting parameters of variable resistors as TKS, functional characteristic, wear resistance, etc.

A semiconductor diode is one of the most popular and widespread components in electronics. What are the parameters of a diode? Where is it applied? What are its varieties? This will be discussed in this article.

What is an inductor and why is it used in electronics? Here you will learn not only about what parameters an inductor has, but also learn how different inductors are indicated on the diagram. The article contains many photographs and images.

In modern pulse technology, the Schottky diode is actively used. How is it different from conventional rectifier diodes? How is it indicated on the diagrams? What are its positive and negative properties? You will learn about all this in the article about the Schottky diode.

The zener diode is one of the most important elements in modern electronics. It is no secret that semiconductor electronics is very demanding on the quality of the power supply, and to be more precise, on the stability of the supply voltage. Here a semiconductor diode comes to the rescue - a zener diode, which is actively used to stabilize the voltage in the nodes of electronic equipment.

What is a varicap and where is it used? In this article, you will learn about an amazing diode that is used as a variable capacitor.

If you're into electronics, you've probably faced the challenge of connecting multiple speakers or loudspeakers. This may be required, for example, when self-assembling acoustic speaker, connecting multiple speakers to a single channel amplifier, and so on. Reviewed 5 good examples. Lots of photos.

The transistor is the basis of modern electronics. His invention revolutionized radio engineering and served as the basis for the miniaturization of electronics - the creation of microcircuits. What is the name of a transistor in a circuit diagram? How to solder the transistor in printed circuit board? You will find answers to these questions in this article.

A composite transistor or in another way the Darlington transistor is one of the modifications of the bipolar transistor. You will learn about where composite transistors are used, about their features and distinctive properties from this article.

When selecting analogues of MIS field-effect transistors, one has to refer to the technical documentation with the parameters and characteristics of a particular transistor. In this article, you will learn about the main parameters of powerful MOSFET transistors.

Currently, field-effect transistors are increasingly being used in electronics. On the circuit diagrams field effect transistor is designated differently. The article talks about the conditional graphic designation field effect transistors on the schematics.

What is an IGBT transistor? Where is it used and how is it arranged? In this article, you will learn about the benefits of insulated gate bipolar transistors, as well as how given type transistors on circuit diagrams.

Among huge amount semiconductor devices there is a dinistor. You can find out how a dinistor differs from a semiconductor diode by reading this article.

What is a suppressor? Protective diodes or suppressors are increasingly being used in electronic equipment to protect it from high-voltage impulse noise. You will learn about the purpose, parameters and methods of using protective diodes from this article.

Resettable fuses are increasingly used in electronic equipment. They can be found in security automation devices, computers, portable devices... In a foreign manner, self-resetting fuses are called PTC Resettable Fuses. What are the properties and parameters of the "immortal" fuse? You will learn about this from the proposed article.

Currently, solid-state relays are increasingly being used in electronics. What is the advantage solid state relays in front of electromagnetic and reed relays? Device, features and types of solid state relays.

In the literature devoted to electronics, the quartz resonator is undeservedly deprived of attention, although this electromechanical component has extremely strongly influenced the active development of radio communication technology, navigation and computer systems.

In addition to the well-known aluminum electrolytic capacitors in electronics, a large number of various electrolytic capacitors with different type dielectric. Among them, for example, tantalum smd capacitors, non-polar electrolytic and tantalum output. This article will help novice radio amateurs to recognize various electrolytic capacitors among all kinds of radio elements.

Along with other capacitors, electrolytic capacitors have some specific properties that must be taken into account when using them in homemade electronic devices, as well as when repairing electronics.

In the period from the end of the 19th to the beginning of the 20th century, there was a rapid rise in scientific and technological development and was marked by progress communication technologies such as: radio, telegraph, telephone. Science in the field of electronics studied and developed the necessary element base for radio signal transmitters.

Primary name for everyone electronic products used in the manufacture of radio receivers, such as "radio components" was chosen. Then this definition was extended to elements that were not directly related to radio.

The fifties of the twentieth century were marked by a new surge of scientific and technological progress, which was associated with the advent of television and the first computers (computers). The evolution in electronics has led to the development and improvement of technology for radar and television. As a result, instead of the previously used lamp technologies, solid-state electronic parts began to be used.

A new step in progress in electronics was caused by the development of electronic calculating machines and the emergence of the first multifunctional computer. Such units were huge and included big number elements and therefore were characterized by increased power consumption and low reliability. It was possible to correct these shortcomings only with the advent of microcircuits, microprocessors and progress in microtechnologies. Today, many companies are engaged in the purchase and processing of radio components obtained from various radio equipment.

Classification of radio components

Electronic components can be classified according to the way they function in a circuit, either passive or active. Each of them has its own unique current-voltage characteristic.

Active radio elements are grouped into two classes, such as: vacuum and semiconductor. Vacuum grade parts are airless containers with electrodes (cathode and anode) inside. They are made of ceramic, metal or glass. The electrodes are coated with a special coating that promotes the release of negatively charged particles into an airless working space. A functional electrode that accumulates negatively charged particles is called an anode. The electron flow between the cathode and the anode is the working matter.

The most common vacuum electronic radio components:

1. A diode is a primitive lamp that includes an anode and a cathode.
2. Triode - a vacuum tube is used as an amplifier, converter and generator of electrical signals. It includes one control grid, an electronic heated cathode and an anode.
3. The tetrode is an amplifying low frequencies shielding lamp.
4. A pentode is an element with shielding properties that amplifies low frequencies. It includes the following parts: an anode, a heated cathode, two conventional control networks and one shielding network. The main negative features of these components are large dimensions and high rate power consumption.

Today, the demand for old radio components is growing every day. The main elements that our organization "Electroradiol Prioksky" buys are:

1. semiconductor diode. An element that has different resistance values, relative to the direction vector of electricity. Its functioning is based on the phenomenon of the electron-hole transition (p- and n-junction) and the connection between semiconductors with different types of mixed conductivity.
2. Photothyristors. A component that converts the light that hits the photocell into an electrical current. This happens due to the procedures performed in the electron-hole transition.
3. Resistor. The main electronic element is an integral part of each microcircuit. It is designed to provide active resistance in the circuit. Refers to passive radio components.
4. Transistor. Basic element in radio engineering. It is used to generate, amplify, transform and switch electrical signals.
5. Capacitor. It is a passive, basic electronic device designed to accumulate charge and electrical energy.
6. Transformer. The component that performs the transformation function alternating current using electromagnetic induction in one or more tape or wire windings entangled in a common magnetic flux. There are two bases on which the work of the transformer is based - this is: an electric current that changes its parameters in a certain period of time, forms an electromagnetic field that changes its characteristics in a certain period of time, which converts the magnetic flux passing through the winding, forms an electromotive force in it.
7. Relay. A device that is designed to connect and disconnect electrical circuit with established changes in input electrical or non-electrical operations or influences.

Nowadays, there are many organizations that have a genuine interest in obsolete and obsolete radio components, microcircuits and are engaged in buying them up. Since the processing and disposal of such radioelements makes it possible to extract expensive non-ferrous metals. The specialized firm "Electroradiol Prioksky" officially buys up Soviet radio components at a decent price.

In the article you will learn about what radio components exist. Designations on the diagram according to GOST will be considered. You need to start with the most common - resistors and capacitors.

To assemble any design, you need to know how the radio components look in reality, as well as how they are indicated on electrical diagrams. There are a lot of radio components - transistors, capacitors, resistors, diodes, etc.

Capacitors

Capacitors are parts that are found in any design without exception. Usually the simplest capacitors are two metal plates. And air acts as a dielectric component. I immediately remember the lessons of physics at school, when the topic of capacitors was covered. Two huge flat round pieces of iron acted as a model. They were brought closer to each other, then moved away. And measurements were taken in each position. It is worth noting that mica can be used instead of air, as well as any material that does not conduct electricity. The designation of radio components on imported circuit diagrams differs from the GOSTs adopted in our country.

Please note that ordinary capacitors do not pass D.C.. On the other hand, it passes through it without much difficulty. Given this property, a capacitor is installed only where it is necessary to separate the variable component in direct current. Therefore, we can make an equivalent circuit (according to Kirchhoff's theorem):

1. When operating on alternating current, the capacitor is replaced by a piece of conductor with zero resistance.
2. When working in a DC circuit, the capacitor is replaced (no, not by capacitance!) With resistance.

The main characteristic of a capacitor is its electrical capacitance. The unit of capacitance is Farad. She is very big. In practice, as a rule, they are used which are measured in microfarads, nanofarads, microfarads. In the diagrams, the capacitor is indicated in the form of two parallel dashes, from which there are taps.

variable capacitors

There is also a type of device in which the capacitance changes (in this case due to the fact that there are movable plates). The capacitance depends on the size of the plate (in the formula S is its area), as well as on the distance between the electrodes. In a variable capacitor with an air dielectric, for example, due to the presence of a moving part, it is possible to quickly change the area. Therefore, the capacitance will also change. But the designation of radio components on foreign schemes is somewhat different. A resistor, for example, is depicted on them as a broken curve.

Permanent Capacitors

These elements have differences in design, as well as in the materials from which they are made. The most popular types of dielectrics can be distinguished:

1. Air.
2. Mica.
3. Ceramics.

But this applies only to non-polar elements. There are also electrolytic capacitors (polar). It is these elements that have very large capacities - from tenths of microfarads to several thousand. In addition to the capacitance, such elements have one more parameter - the maximum voltage value at which its use is allowed. These parameters are written on the diagrams and on the capacitor cases.

on the diagrams

It is worth noting that in the case of using trimmer or variable capacitors, two values ​​\u200b\u200bare indicated - the minimum and maximum capacitance. In fact, on the case you can always find a certain range in which the capacitance changes if you turn the axis of the device from one extreme position to another.

Let's say there is variable capacitor with a capacitance of 9-240 (default measurement in picofarads). This means that with a minimum overlap of the plates, the capacitance will be 9 pF. And at the maximum - 240 pF. It is worth considering in more detail the designation of radio components on the diagram and their name in order to be able to read the technical documentation correctly.

Connection of capacitors

We can immediately distinguish three types (there are just so many) connections of elements:

1. Sequential- the total capacity of the entire chain is quite simple to calculate. In this case, it will be equal to the product of all the capacities of the elements, divided by their sum.
2. Parallel- in this case, it is even easier to calculate the total capacity. It is necessary to add the capacitances of all capacitors in the chain.
3. mixed- in this case, the scheme is divided into several parts. We can say that it is simplified - one part contains only parallel-connected elements, the second - only in series.

And that's just general information about capacitors, in fact, you can talk a lot about them, cite entertaining experiments as an example.

Resistors: general information

These elements can also be found in any design - even in a radio receiver, even in a control circuit on a microcontroller. This is a porcelain tube, on which a thin film of metal (carbon - in particular, soot) is deposited on the outside. However, even graphite can be applied - the effect will be similar. If the resistors have a very low resistance and high power, then it is used as a conductive layer

The main characteristic of a resistor is its resistance. Used in electrical circuits to set the required current value in certain circuits. At physics lessons, a comparison was made with a barrel filled with water: if you change the diameter of the pipe, you can adjust the speed of the jet. It should be noted that the resistance depends on the thickness of the conductive layer. The thinner this layer, the higher the resistance. Wherein conventions radio components in the diagrams do not depend on the size of the element.

Fixed resistors

As for such elements, the most common types can be distinguished:

1. Metallized lacquered heat-resistant - MLT for short.
2. Moisture resistant resistance - sun.
3. Carbon lacquered compact - ULM.

Resistors have two main parameters - power and resistance. The last parameter is measured in ohms. But this unit of measurement is extremely small, so in practice you will often find elements whose resistance is measured in megaohms and kiloohms. Power is measured exclusively in watts. Moreover, the dimensions of the element depend on the power. The larger it is, the larger the element. And now about what is the designation of radio components. On the diagrams of imported and domestic devices, all elements can be designated differently.

On domestic circuits, a resistor is a small rectangle with an aspect ratio of 1: 3, its parameters are written either on the side (if the element is located vertically) or on top (in the case of a horizontal arrangement). First, the Latin letter R is indicated, then the serial number of the resistor in the circuit.

Variable resistor (potentiometer)

Constant resistances have only two outputs. But there are three variables. On the electrical diagrams and on the body of the element, the resistance between the two extreme contacts is indicated. But between the middle and any of the extremes, the resistance will vary depending on the position in which the axis of the resistor is located. Moreover, if you connect two ohmmeters, you can see how the reading of one will change down, and the second - up. You need to understand how to read circuit diagrams of electronic devices. The designations of radio components will also not be superfluous to know.

The total resistance (between the extreme terminals) will remain unchanged. Variable resistors are used to control the gain (with their help you change the volume in radios, TVs). Besides, variable resistors widely used in automobiles. These are fuel level sensors, electric motor speed controllers, lighting brightness.

Connection of resistors

In this case, the picture is completely opposite to that of the capacitors:

1. serial connection- the resistance of all elements in the circuit is added.
2. Parallel connection The product of the resistances is divided by the sum.
3. mixed- the whole scheme is divided into smaller chains and calculated step by step.

On this, you can close the review of resistors and begin to describe the most interesting elements - semiconductors (the designations of radio components in the diagrams, GOST for UGO, are discussed below).

Semiconductors

This is the largest part of all radio elements, since semiconductors include not only zener diodes, transistors, diodes, but also varicaps, varicondas, thyristors, triacs, microcircuits, etc. Yes, microcircuits are one crystal that can contain a great variety of radio elements - and capacitors, and resistances, and pn-junctions.

As you know, there are conductors (metals, for example), dielectrics (wood, plastic, fabrics). There may be different designations of radio components in the diagram (a triangle is most likely a diode or a zener diode). But it is worth noting that a triangle without additional elements denotes a logical ground in microprocessor technology.

These materials either conduct current or they don't, regardless of the state of aggregation they are in. But there are also semiconductors, the properties of which vary depending on specific conditions. These are materials such as silicon, germanium. By the way, glass can also be partly attributed to semiconductors - in its normal state it does not conduct current, but when heated, the picture is completely opposite.

Diodes and zener diodes

A semiconductor diode has only two electrodes: a cathode (negative) and an anode (positive). But what are the features of this radio component? You can see the designations on the diagram above. So, you connect the power supply with a plus to the anode and a minus to the cathode. In this case, electric current will flow from one electrode to another. It is worth noting that the element in this case has extremely low resistance. Now you can conduct an experiment and connect the battery in reverse, then the current resistance increases several times, and it stops flowing. And if you direct an alternating current through the diode, you will get a constant output (though with small ripples). When using a bridge switching circuit, two half-waves (positive) are obtained.

Zener diodes, like diodes, have two electrodes - a cathode and an anode. AT direct connection this element works in exactly the same way as the diode discussed above. But if you start the current in the opposite direction, you can see a very interesting picture. Initially, the zener diode does not pass current through itself. But when the voltage reaches a certain value, a breakdown occurs, and the element conducts current. This is the stabilization voltage. A very good property, thanks to which it is possible to achieve a stable voltage in the circuits, to completely get rid of fluctuations, even the smallest ones. The designation of radio components on the diagrams is in the form of a triangle, and at its top there is a line perpendicular to the height.

transistors

If diodes and zener diodes can sometimes not even be found in designs, then you will find transistors in any (except Transistors have three electrodes:

1. Base (abbreviated as the letter "B" is indicated).
2. Collector (K).
3. Emitter (E).

Transistors can operate in several modes, but most often they are used in amplifying and key (like a switch). You can make a comparison with a mouthpiece - they shouted into the base, an amplified voice flew out of the collector. And hold on to the emitter with your hand - this is the case. The main characteristic of transistors is the gain (the ratio of the collector and base current). It is this parameter, along with many others, that is the main one for this radio component. Designations on the diagram for the transistor - vertical bar and two lines approaching it at an angle. There are several most common types of transistors:

1. Polar.
2. Bipolar.
3. Field.

There are also transistor assemblies, consisting of several amplifying elements. These are the most common radio components. The designations on the diagram were discussed in the article.

The simplest elements of electronic devices are:

1) Capacitor- a device capable of storing energy in an electric field.

The current flowing through the capacitor is proportional to the change in voltage per unit time.

2) Throttle or an inductor - the choke also has the ability to store energy, but not in an electric, but in a magnetic field. It behaves like a capacitor, except that it's not voltage that needs to be considered, but current.

If you connect a choke and a capacitor in parallel, you get an oscillatory circuit.

3) Diode (p-n junction) - two-electrode electronic device, has different conductivity depending on the direction of the electric current

P has electronic conductivity (leaded by a donor impurity)

N has hole conductivity (leaded by an accentor impurity)

There are several types of diodes:

zener diode

• photo and LEDs

4) Resistor- a passive element of an electrical circuit, ideally characterized only by resistance to electric current, that is, for an ideal resistor, Ohm's law must be fulfilled at any time.

Ohm's law states that current is equal to the ratio of voltage to resistance (I=U/R)

a) Voltage is a potential difference.

b) Resistance - the value is inversely proportional to the conductivity.

Voltage is measured in volts, resistance is in ohms.

1. passive schemes. Resistive divider.

Voltage divider - a device for dividing direct or alternating voltage.

It is built on the basis of active, reactive or non-linear resistances.

1) Divider. In the divider, the resistances are connected in series.

The output voltage is the voltage across separate area divider circuits.

2) Shoulder. The sections located between the supply voltage and the point of removal of the output voltage are called the shoulders of the divider.

a) Shoulder lower. The shoulder between the output and the zero supply potential is usually called the lower one.

b ) Shoulder upper. The other is called the top. Any divider has two arms.

3) resistor divider. A voltage divider built solely on active resistances is called a resistive voltage divider. The division factor of such dividers does not depend on the frequency of the applied voltage.

The simplest resistive divider voltage is two series-connected resistors R1 and R2 connected to a voltage source U.

1. passive filters. Fnch.

1) Passive filter- an electronic filter consisting only of passive components such as, for example, capacitors and resistors.

Passive filters do not require any energy source to operate.

Unlike active filters, passive filters do not amplify the signal in terms of power. Almost always passive filters are linear.

2) Usage. Passive filters are used throughout radio and electronic equipment, such as loudspeakers, uninterruptible power supplies, etc.

3) Low Pass Filter (LPF)- an electronic or any other filter that effectively passes the frequency spectrum of a signal below a certain frequency (cutoff frequency), and reduces (or suppresses) the signal frequencies above this frequency.

The degree of suppression of each frequency depends on the type of filter.

3) Difference from HPF. In contrast, the high-pass filter passes signal frequencies above the cutoff frequency, attenuating low frequencies.

4) Terms"high frequencies" and "low frequencies" as applied to filters are relative and depend on the chosen structure and filter parameters.

5) Ideal low pass filter Completely suppresses all frequencies of the input signal above the cutoff frequency and passes all frequencies below the cutoff frequency unchanged. There is no transition zone between the frequencies of the suppression band and the passband. An ideal low-pass filter can only be realized theoretically

The main indicator of the perfection of electronic equipment is the packing density, i.e. the number of circuit elements in 1 cm3 of the operating device.

Manufacturing technology integrated circuits provides a packing density of several thousand elements per 1 cm3.

Resistors

Resistors are the most common elements and have the following graphic symbol (UGO):

Resistors are made of conductive material: graphite, thin metal film, wires with low conductivity.

The resistor is characterized by the resistance value: R \u003d U / I, as well as the power that the resistor dissipates into space, tolerance, temperature coefficient, noise level. The industry produces resistors with resistance from 0.01 ohm to 1012 ohm and power from 1/8 to 250 W with a tolerance of 0.005% to 20%. Resistors are used as load and current-limiting resistances, voltage dividers, additional resistances, shunts.

Capacitors

Capacitor - a device with two terminals and having the property:

where
• C is the capacitance in farads;
• U - voltage in volts;
• Q - charge in pendants.

The UGO of the capacitor is as follows:

The industry produces ceramic, electrolytic and mica capacitors with a capacitance from 0.5 pF to 1000 microfarads and a maximum voltage of 3V to 10 kV.

Capacitors are used in oscillatory circuits, filters, for separating DC and AC circuits, as blocking elements. In AC circuits, a capacitor behaves like a resistor whose resistance decreases with increasing frequency.

Inductors

An inductor is a device that has the property:

U = L dI / dt,

where
• L is the inductance in henry (or mH or µH);
• U - voltage in volts;
• dI/dt - rate of current change.

The UGO inductors are as follows:

An inductor is an insulated conductor coiled into a spiral, which has a significant inductance with a relatively small capacitance and low active resistance. The core material is usually iron or ferrite in the form of a bar, a torus.

In AC circuits, the coil behaves like a resistor whose resistance increases with increasing frequency.

A transformer is a device consisting of two inductively coupled inductors, called primary and secondary windings.

UGO transformer with magnetic core:

Transformation ratio:

where w1 and w2 are the number of turns

Transformers are used to convert alternating voltages and currents, as well as to isolate from the network.

Semiconductors

The action of semiconductor devices is based on the use of the properties of semiconductors.

The number of currently known semiconductor materials is quite large. For the manufacture of semiconductor devices, simple semiconductor substances are used - germanium, silicon, selenium - and complex semiconductor materials - gallium arsenide, gallium phosphite and others. The values ​​of electrical resistivity in pure semiconductor materials range from 0.65 ohm m (germanium) to 108 ohm m (selenium).

Semiconductors or semiconductor compounds are either intrinsic (pure) or doped (doped). In pure semiconductors, the concentration of charge carriers - free electrons and holes is only 10 16 - 1018 per 1 cm3 of the substance.

To reduce the resistivity of a semiconductor and give it a certain type of electrical conductivity - electronic with a predominance of free electrons or hole with a predominance of holes - certain impurities are introduced into pure semiconductors. This process is called doping. Elements of groups 3 and 5 are used as dopants periodic system elements of D. I. Mendeleev. Alloying elements of group 3 create hole electrical conductivity of semiconductor materials and are called acceptor impurities, elements of group 5 - electronic electrical conductivity are called donor impurities.

Intrinsic semiconductors are semiconductors in which there are no impurities (donors and acceptors). At T = 0, there are no free charge carriers in the intrinsic semiconductor, and the concentration of charge carriers is N n = Np = 0 and it doesn't conduct electricity. At T > 0, some of the electrons are thrown from the valence band into the conduction band. These electrons and holes can move freely through the energy bands. In practice, doped semiconductors are used. The electrical resistivity of a doped semiconductor substantially depends on the impurity concentration. At an impurity concentration of 1020 - 1021 per cm3 of substance, it can be reduced to 5 · 10-6 Ohm m for germanium and 5 · 10-5 Ohm m for silicon.

When an electric field is applied to a doped semiconductor, an electric current flows in it.

Semiconductor resistors

A semiconductor resistor is a two-terminal semiconductor device that uses the dependence of the electronic resistance of a semiconductor on voltage, temperature, illumination, and other control parameters.

In semiconductor resistors, a semiconductor is used that is uniformly doped with impurities. Depending on the type of impurities and the design, it is possible to obtain different dependences on the control parameters.

A linear resistor is a semiconductor resistor that uses a lightly doped material such as silicon or gallium arsenide.

The electrical resistivity of such a semiconductor depends little on the electric field strength and electric current density. Therefore, the resistance of a linear semiconductor resistor remains almost constant over a wide range of voltages and currents. Semiconductor linear resistors are widely used in integrated circuits.

Current-voltage characteristic of a linear resistor

Nonlinear resistive elements

UGO of a nonlinear resistive element is shown in the figure:

Current I flowing through a non-linear element, voltage U across it. Dependence U(I) or I(U) is called current-voltage characteristic.

Varistors

Resistive elements whose resistance depends on the strength of the electric field are called varistors. Varistors are made from pressed grains of silicon carbide. The electrical conductivity of the material is mainly due to the breakdown of oxide films covering the grains. It is determined by the strength of the applied electric field, i.e. depends on the magnitude of the applied voltage.

Conditional graphic representation of the varistor and its volt-ampere characteristics shown in the picture:

Varistors are characterized rated voltage Unom , rated current Inom , as well as non-linearity coefficient β. This coefficient is equal to the ratio of static resistance to differential resistance at the point of the characteristic with nominal values ​​of voltage and current:

,

where U and I are the voltage and current of the varistor. Non-linearity coefficient for various types of varistors within 2 - 6

Thermistors

A large group of non-linear resistive elements are controlled non-linear elements. These include thermistors (thermistors) - non-linear resistive elements, the current-voltage characteristics of which depend significantly on temperature. In some types of thermistors, the temperature is changed by a special heater. Thermistors are made either from metal (copper, platinum), the resistance of which changes significantly with temperature, or from semiconductors. In semiconductor thermistors, the dependence of resistance on temperature is described by an analytical function

.

Here R(T0) is the value of the static resistance at a temperature T0 = 293 K, where T is the absolute temperature and B is the coefficient. The conventional graphic designation of the thermistor, its temperature characteristic, current-voltage characteristic is shown in the figure:

There are two types of thermistors: a thermistor, whose resistance decreases with increasing temperature, and a posistor, whose resistance increases with increasing temperature. The letter designation of the thermistor with a negative temperature coefficient is TP, and with a positive coefficient - TRP. Temperature coefficient TKS = , where R1 is the resistance at nominal temperature, ΔR is the change in resistance when the temperature changes by Δt.

Structurally, thermistors are made in the form of beads, washers, disks.

Photoresistors

A photoresistor is a semiconductor resistor whose resistance depends on the light flux incident on a semiconductor material or on penetrating electromagnetic radiation. The most widespread are photoresistors with a positive photoelectric effect (for example, SF2-8, SF3-8). The UGO of such an element is shown in the figure:

In photoresistors, the resistance changes as a result of irradiating a wafer of semiconductor material with a light flux in the visible, ultraviolet or infrared range. Sulfides of thallium, tellurium, cadmium, lead, bismuth are used as the material.

The current-voltage characteristics of photoresistors are linear functions, the angle of inclination of which depends on the magnitude of the luminous flux. In the coordinates I - U (vertical current), the angle made by a straight line with the horizontal axis (voltage axis), the greater, the greater the luminous flux. The dark resistance of resistor optocouplers is 10 7 - 109 Ohm. In the illuminated state, it drops to several hundred ohms. Their performance is not high and is limited to values ​​​​of a few kilohertz.

magnetoresistors

Magnetoresistors are semiconductor materials whose electrical resistance depends on the strength of the magnetic field acting on the material. The material used is bismuth, germanium, etc. The resistance of the magnetoresistor is described by the dependence

,

where R(0) is the resistance at H = 0; α is the coefficient, H is the strength of the magnetic field in which the magnetoresistor is placed.

Semiconductor diodes

Semiconductor diodes are one of the most common subclasses of semiconductor devices. They are distinguished by a variety of fundamental physical principles, a variety of semiconductor materials used, and a variety of design and technological implementations. Semiconductor diodes according to their functional purpose can be divided into:

1. Rectifiers (including poles, bridges, matrices), impulse, zener diodes, varicaps, controlled valves (thyristors, symmetric thyristors - triacs, dinistors);
2. microwave diodes: detector, mixing, parametric, pin diodes, avalanche, tunnel diodes, Gunn diodes;
3. Optoelectronic: photodiodes, LEDs, IR emitters, laser diodes based on heterostructures;
4. Magnetic diodes.

Lightly doped semiconductors are used to make low-power diodes, while heavily doped ones are used to make high-power and impulsive diodes.

The electron-hole junction, which for brevity is called the p-n junction, is of primary importance for the operation of semiconductor diodes.

Electron-hole p-n junction

An electron-hole, or p-n junction, is the contact of two semiconductors of the same type with various types conductivity (electronic and hole). Classic example p-n transitions are: n-Si - p-Si, n-Ge - p-Ge.

Recombination (reunification) of electrons and holes occurs in the boundary layer. Free electrons from the band of an n-type semiconductor occupy free levels in the valence band of a p-type semiconductor. As a result, a layer is formed near the boundary of two semiconductors, which is devoid of mobile charge carriers and, therefore, has a high electrical resistance, the so-called barrier layer. The thickness of the barrier layer usually does not exceed a few micrometers.

The expansion of the barrier layer is prevented by immobile ions of donor and acceptor impurities, which form a double electric layer at the boundary of the semiconductors. This layer determines the contact potential difference (potential barrier) at the semiconductor interface. The resulting potential difference creates an electric field in the blocking layer, which prevents both the transition of electrons from the n-type semiconductor to the p-type semiconductor, and the transition of holes to the n-type semiconductor. At the same time, electrons can move freely from a p-type semiconductor to an n-type semiconductor, just like holes can move from an n-type semiconductor to a p-type semiconductor. Thus, the contact potential difference prevents the movement of major charge carriers and does not prevent the movement of minority charge carriers. However, when minority carriers move through the p-n junction (the so-called drift current Idr), the contact potential difference φk decreases, which allows some of the main carriers with sufficient energy to overcome the potential barrier due to the contact potential difference φk. A diffuse current Idif appears, which is directed towards the drift current Idr, i.e. there is a dynamic equilibrium in which Idr = Idif .

If an external voltage is applied to the p-n junction, which creates an electric field of strength Evn in the blocking layer, coinciding in direction with the field of immobile ions with strength Ezap, this will only lead to expansion of the blocking layer, since it will divert both positive and negative charge carriers from the contact zone (holes and electrons).

In this case, the resistance of the pn junction is high, the current through it is small - it is due to the movement of minority charge carriers. In this case, the current is called reverse (drift), and the p-n junction is closed.

With the opposite polarity of the voltage source, the external electric field is directed towards the field of the double electric layer, the thickness of the barrier layer decreases, and at a voltage of 0.3 - 0.5 V, the barrier layer disappears. The resistance of the p-n junction drops sharply and a relatively large current arises. The current is called direct (diffusion), and the transition is open.

The resistance of an open p-n junction is determined only by the resistance of the semiconductor.

Classification of diodes

A semiconductor diode is a non-linear electronic device with two electrodes. Depending on the internal structure, type, quantity and level of doping of the internal elements of the diode and the current-voltage characteristic, the properties of semiconductor diodes are different.

Conventional graphic designations of some types of diodes according to domestic standards and their graphic images shown in the table:

Rectifier Diodes

Designed to convert alternating current into unipolar pulsating or direct current. Such diodes are not subject to high requirements for speed, stability of parameters, and capacitance of p-n junctions. Due to the large area of ​​the p-n-junction, the barrier capacitance of the diode can reach tens of picofarads.

Figure a shows a p-n junction that forms a diode, figure b shows the inclusion of a diode in the forward direction, in which current Ipr flows through the diode. The figure in shows the inclusion of the diode in the opposite direction, at which the current Iobr flows through the diode.

Figure a shows the inclusion of the diode VD in a circuit fed by a sinusoidal EMF source e, the time characteristic of which is shown in figure b. Figure c shows a graph of the current flowing through a diode.

The main parameters of a rectifier diode are:

• Uobr.max - maximum allowable voltage, applied in the opposite direction, which does not violate the diode's performance;
• Ivp.sr - the average value of the rectified current for the period;
• Ipr.i - the amplitude value of the pulsed current for a given duration of the duty cycle of the pulse;
• Iobr.sr - the average value of the reverse current for the period;
• Upr.sr - the average value of the forward voltage across the diode for the period;
• Pav is the average power dissipated by the diode over the period;
• rdif - differential resistance of the diode.

Qualitatively, the current-voltage characteristics of a universal silicon and germanium diode are shown in Figure a, and the dependences of the current-voltage characteristics of a universal silicon diode for three temperatures are shown in Figure b.

For safe operation of the germanium diode, its temperature should not exceed 85°C. Silicon diodes can operate at temperatures up to 150°C.

Pulse Diodes

Designed for work in circuits with pulse signals. The main for them is the mode of transient processes. To reduce the duration of transient processes in the device itself, pulsed diodes have small p-n-junction capacitances, which range from fractions to units of picofarads.

This is achieved by reducing the area of ​​the p-n-junction, which in turn leads to small values ​​of the allowable power dissipated by the diode. The main characteristics of pulse diodes are:

• Upr.max - the maximum value of the pulse forward voltage;
• Ipr.max - the maximum value of the pulsed current;
• Cd - diode capacitance;
• tset - the time of establishing the forward voltage of the diode;
• tres is the recovery time of the reverse resistance of the diode. This is the time interval from the moment the current passes through zero until the moment when the reverse current reaches a predetermined small value.

zener diodes

To stabilize the voltage in electrical circuits, semiconductor diodes with special current-voltage characteristics are used - zener diodes. The volt-ampere characteristic of the zener diode is shown in the figure. The reverse branch of the current-voltage characteristic indicates operation in the electrical breakdown mode and contains a section between points a and b, close to linear and oriented along the current axis. In this mode, with a significant change in the current of the zener diode, the voltage does not change significantly.

This section for the zener diode is working. When the current changes in the range from Ict.min to Ist.max, the voltage across the diode differs little from the value Ust.

The value of Ist.max is limited by the maximum allowable power dissipation of the zener diode. Minimum value stabilization current in absolute value to be greater than the value of Ict.min, at which the zener diode retains its stabilizing properties.

The industry produces a wide range of zener diodes with a stabilization voltage from 1V to 180V.

The zener diode is characterized by the following parameters:

• Ust - stabilization voltage;
• Ist.max - maximum stabilization current;
• Ict.min - minimum stabilization current;
• rd - differential resistance in the section "ab";
• TKN - temperature coefficient of stabilization voltage.

Zener diodes are designed to stabilize the voltage on the load with a changing voltage in the external circuit. The zener diode is a fast device and works well in pulse circuits.

Diodes Schottky

Schottky diodes are characterized by a low voltage drop across the open diode. The value of this voltage is about 0.3V, which is much less than that of conventional diodes. In addition, the reverse resistance recovery time ts is on the order of 100 ps, ​​which is much less than that of conventional diodes. Except digital circuits Schottky diodes are used in secondary power supply circuits in order to reduce static and dynamic losses in the diodes themselves: in the output stages of impulsive power supplies, DC / DC convectors, in computer power supply systems, servers, communication and data transmission systems.

Varicaps

Nonlinear capacitors based on the use of the properties of an electron-hole p-n junction are varicaps. A varicap is used when a reverse voltage is applied to a p-n junction. The width of the pn junction, and hence its capacitance, depends on the magnitude of the voltage applied to the pn junction. The capacitance of such a capacitor is determined using the expression

In this expression, is the capacitance at zero blocking voltage, S and l are the area and thickness of the p-n junction, ε0 is the dielectric constant, ε 0 = 8.85 10-12 F/M, εr - relative dielectric constant; φк - contact potential (for germanium 0.3..0.4 V and 0.7..0.8 V for silicon); |u| - reverse voltage module applied to the p-n-junction; n = 2 for abrupt transitions; n = 3 for main transitions.

The C(u) dependence graph is shown in the figure

The maximum capacitance value of the varicap is at zero voltage. As the reverse bias increases, the capacitance of the varicap decreases. The main parameters of the varicap are:

• C - capacitance at reverse voltage 2 - 5 V;
• To C = Cmax / Cmin- capacitance overlap coefficient.

Usually C \u003d 10 - 500 pF, KC \u003d 5 - 20. Varicaps are used in remote control systems, for automatic frequency control, in parametric amplifiers with a low level of intrinsic noise.

LEDs

An LED, or emitting diode, is a semiconductor diode that emits light quanta when a direct current flows through it.

LEDs are divided into two groups according to their emission characteristics:

• LEDs by radiation in the visible part of the spectrum;
• LEDs emitting in the infrared part of the spectrum.

A schematic representation of the structure of the LED and its UGO is shown in the figure:

The areas of application of IR LEDs are optoelectronic switching devices, optical communication lines, and remote control systems. The currently most common infrared source is the GaAs LED (λ = 0.9 µm). The ability to create economical and long-lasting LEDs that are spectrally matched to natural light and the sensitivity of the human eye opens up new perspectives for their non-traditional uses. Among them, the use of LEDs in multi-section traffic lights, individual micro-power lighting bulbs (with a power of 3 W, the luminous flux is 85 lm), in car lighting fixtures.

Photodiodes

In photodiodes based on p-n junctions, the effect of separation at the boundary of the electron-hole junction of minor non-equilibrium carriers created by optical radiation is used. Schematically, the photodiode is shown in the figure:

When a light quantum with energy hγ hits in the intrinsic absorption band, a pair of nonequilibrium carriers arises in a semiconductor - an electron and a hole. When registering an electrical signal, it is necessary to register the change in carrier concentrations. As a rule, the principle of registration of minor charge carriers is used.

When the external circuit is open (SA open, R = ∞), for the case when there is no external voltage, no current flows through the external circuit. In this case, the voltage at the outputs of the photodiode will be maximum. This value VG is called open circuit voltage Vxx. The voltage Vxx (photo EMF) can also be determined directly by connecting a voltmeter to the outputs of the photodiode, but the internal resistance of the voltmeter must be much greater than the resistance of the pn junction. In the short circuit mode (SA is closed), the voltage at the terminals of the photodiode VG = 0. The short circuit current Isc in the external circuit is equal to the photocurrent If

Ikz \u003d If

The figure shows the CVC family of a photodiode with both negative and positive polarity of the photodiode.

With positive VG voltages, the photodiode current increases rapidly (forward direction) with increasing voltage. When illuminated, the total forward current through the diode decreases, since the photocurrent is directed opposite to the current from an external source.

CVC p-n-junction, located in the 2nd quadrant (VG> 0, I< 0), показывает, что фотодиод можно использовать как источник тока. На этом базируется принцип работы solar panels based on p-n junctions (photogenerator mode). The light characteristic is the dependence of the photocurrent Iph on the light flux Ф incident on the photodiode. This also includes the dependence of Vxx on the magnitude of the luminous flux. The number of electron-hole pairs formed in the photodiode during illumination is proportional to the number of photons incident on the photodiode. Therefore, the photocurrent will be proportional to the magnitude of the luminous flux:

If \u003d kF,

where K - coefficient of proportionality, depending on the parameters of the photodiode.

When the photodiode is reverse biased, the current in the external circuit is proportional to the luminous flux and does not depend on the voltage VG (photoconverter mode). Photodiodes are fast devices and operate at frequencies of 107 - 1010 Hz. Photodiodes are widely used in LED-photodiode optocouplers.

Optocoupler (optocoupler)

An optocoupler is a semiconductor device containing a radiation source and a radiation receiver, combined in one package and interconnected optically, electrically, or simultaneously by both connections. Optocouplers are very widespread, in which a photoresistor, a photodiode, a phototransistor and a photothyristor are used as a radiation receiver.

In resistor optocouplers, the output resistance can change by 107 ..108 times when the input circuit mode changes. In addition, the current-voltage characteristic of the photoresistor is highly linear and symmetrical, which determines the wide applicability of rubber optocouplers in similar devices. The disadvantage of resistor optocouplers is low speed - 0.01..1 s.

In the transmission circuits of digital information signals, mainly diode and transistor optocouplers are used, and thyristor optocouplers are used for optical switching of high-voltage high-current circuits. The speed of thyristor and transistor optocouplers is characterized by switching time, which often lies in the range of 5..50 µs. For some optocouplers, this time is shorter. Let's take a closer look at the LED-photodiode optocoupler.

The conventional graphic designation of the optocoupler is shown in Figure a:

The emitting diode (left) must be turned on in the forward direction, and the photodiode - in the forward (photogenerator mode) or in the opposite direction (photoconverter mode).