Electronics lessons

Максим Исаев
Reading time: 8 min
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Изучение электронной техники полупроводниковых приборов является важным и необходимым условием для уThe study of electronic technology of semiconductor devices is an important and necessary condition for a successful repair. Having successfully mastered the lessons of electronics, you will learn to understand the processes occurring in semiconductors. The vast majority of electronic devices are built on the basis of transistors. 

Semiconductors

To build electronic circuits, together with passive elements, semiconductor devices are used, made from materials occupying intermediate positions between metals and dielectrics. A metal conducts electricity, but a dielectric does not. This is due to their chemical properties – the location of the valence band and the conduction band.

There are much more semiconductors in nature than metals and dielectrics. These include Si (silicon), Ge (germanium), GaS (gallium arsenide), etc. Semiconductors change their properties under the influence of external factors – heating, cooling, the introduction of various impurities. These properties are used to manufacture semiconductor devices.

P-N transition

The most common semiconductor element is silicon. At the lessons of electronics, we will study the crystalline structure of materials, we will analyze in detail what a P-N junction is. It is also called “electron-hole” transition. Impurities are introduced into the semiconductor to work. 

There are two types of P-N transitions:

  • acceptor
  • donor

Impurity atoms replace the main atoms of the crystal lattice.

The boundary layer between two regions of materials with different impurities form an electrical junction. This transition is called the P-N transition. Thus, a P-N junction is a transition between two regions of a semiconductor having a different type of conductivity.

P-N переход
P-N transition

When a voltage is applied to the P-N junction “+” to the P-region and “-” to the N-region, an electric current will flow. If the voltage is reversed, no current will flow. This is due to the manufacturing technology and properties of the semiconductor. Based on the work of the P-N junction, a semiconductor element was invented – the Diode.   

Diode

Electronics lessons are aimed at studying a semiconductor device with one P-N junction and two terminals, which is called a diode. The properties of the P-N junction described above apply to a diode. The most widely used are germanium and silicon semiconductor devices. 

Схема диода
Diode circuit

Diodes are classified by:

  • appointment
  • designs
  • current
  • voltage
  • frequency
  • other parameters

There are various types of diodes: pulse, tunnel, rectifier and many others. Rectifiers are used to rectify AC to DC. Pulse are used to work in pulse circuits, have a low capacitance P-N junction. Tunnel found application in high frequency generators.

In addition to diodes, there are their varieties: photodiodes, LEDs, zener diodes.

A zener diode is a Zener diode, where the voltage in the electrical breakdown region does not depend on

current. These devices are used to stabilize the voltage. LEDs and photodiodes have the effect of optical radiation in the visible or infrared spectrum, are used for indication or in remote control systems.

Diode bridge

The diode bridge consists of 4 diodes. An alternating voltage is applied to the diagonal of the bridge. It is designed to convert AC voltage to DC. At the output of the bridge after rectification, half-cycles of the rectified voltage appear. They are shaped like truncated sinusoids.

An alternating voltage of a positive half-wave is applied to the input. At this moment, the VD1 diode opens, the current flows through the load in a certain direction and exits through the VD4 diode into the network line. When a negative half-wave arrives, VD2 opens and the current flows through the load in the same direction as in the first case. Leaves the line through VD3.

It follows from this that the current in the load always flows in one direction. And the output voltage has the shape shown in the graph below (Uout (t)).

Диодный мост

Transistor

A transistor is a semiconductor device that has two or more P-N junctions. It has three outputs, designed for signal amplification (analog circuits), key modes (digital circuits), signal generation and conversion. There are bipolar and field-effect transistors.

Транзисторы
Transistors

Designation of conclusions of bipolar transistors:

  • Base (B)
  • Collector
  • Emitter (E)

Designation of the findings of field-effect transistors:

  • Shutter (G)
  • Stock (D)
  • Source (S)

Bipolar transistors have different conduction structures P-N-P and N-P-N. This type of semiconductor devices have various switching schemes in electronic circuits:

  • with a common base (OB)
  • common emitter (CE)
  • common manifold (OK)

The name of the inclusion comes from that electrode of the bipolar transistor, which is common to the input and output circuits. A common switching circuit is the common emitter circuit.

N-P-N переход
N-P-N transition

A field effect transistor is a semiconductor device. Its work is due to the current of the main charge carriers – charges of the same sign of electrons or “holes”. This type of transistor has the following advantages over bipolar ones:

  • input high impedance
  • low control power
  • work at low temperatures
  • can work well at high frequencies

This type of transistors is divided into transistors with a control P-N junction and with an insulating gate.

There are two types of isolation gate transistors:

  • with built-in channel (the channel is created during the manufacturing process)
  • induced channel which is created under the action of voltage applied to the electrodes of the transistor.

Данный вид транзисторов нашел широкое применение в электронной технике (блоки питания майнеров, сварочные аппараты, LED-подсветка, различные виды памяти и т.д.).

An induced channel transistor has the following structure:

  • substrate – a plate of lightly doped silicon. Heavily doped regions with a semiconductor are created in the substrate.
  • stock (D)
  • source(S)
  • shutter (G)
Структура транзистора со встроенным каналом
The structure of a transistor with an embedded channel

Under the action of a voltage application at the dielectric-semiconductor interface, an electron-rich layer is induced. Thus a channel is formed. Therefore, in the initial state (no applied voltage), there is no channel between the drain and the source of the transistor.

Due to the manufacturing structure, these types of transistors are often called MIS or MOS transistors. What does it mean – metal, dielectric, semiconductor or metal, oxide, semiconductor.

Field-effect transistors, like bipolar ones, can be switched on:

  • with a common source (OI)
  • with common drain (OS) – source follower
  • with common gate(OZ)

MIS structures are widely used in memory chips since miniaturization sizes have been reached, where this type of device is increasingly used in the field of nanotechnological developments and miniaturization of devices, as well as their speed.

Thyristors are electronic devices with a four-layer structure. They consist of P-N junction areas connected one after the other. Devices with two outputs are called dinistors. A device with three outputs is called a thyristor (triac, which, unlike a thyristor, works in two directions).

Тиристор
Thyristor

Thyristors (triacs) have the following conclusions:

  • anode
  • cathode
  • control electrode

At present, thyristors are mainly used in power electronics as powerful controlled switches of power electrical circuits.

Thyristors have allowable values ​​of currents and voltages, turn-on and turn-off times.

Optoelectronic devices

Electronics lessons are devoted to the study of various elements of semiconductors. It can be seen that many of them may depend on external environmental phenomena, for example, light. This section is studied by optoelectronics, i.e. interaction of electromagnetic waves with electrons, as well as a method for creating optoelectronic devices.

Оптоэлектроника
Optoelectronics

The main elements of optoelectronics are:

  • lasers
  • IR diodes
  • UV diodes
  • photodiodes
  • phototransistors
  • fiber optic systems

LEDs

LEDs are diodes containing a P-N junction. Where, when an electric current passes, optical radiation is generated, which accompanies the recombination of carriers. The color of the glow depends on the semiconductor impurity.

Светодиод
Light-emitting diode

Photoresistors – change resistance under the influence of radiation.

Photodiode – has the property of one-way conduction, which has arisen when exposed to optical radiation. It is used to convert an optical signal into an electrical one.

Phototransistor – usually bipolar, the collector current is controlled based on the photoelectric effect and serves to convert light signals into electrical ones.

An optocoupler is a device consisting of a light emitter and a photodetector interacting with each other, placed in one housing. With the help of an optocoupler, galvanic isolation, separation of circuits is carried out. They are widely used in automation, power supplies, frequency converters and many other electronic devices.

Conclusions

  • Electronics lessons contribute to understanding the operation of the element base, which allows you to repair electronic devices with confidence.
  • We study the principle of operation and algorithms for diagnosing transistors and other semiconductor devices in the classroom in radio engineering and circuitry.
  • Reading circuits and designing electronics is possible only with a confident understanding of semiconductor designs. 
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