Electronic amplifiers are special devices that increase the power, voltage or current of incoming signals. Their exact purpose and principles of operation depend on the specific type of device, of which there are quite a lot. They are used in recording studios, television and radio, and help in receiving Wi-Fi signals and signals from space. And this is not the whole list of functions, because it is difficult to overestimate the value of these devices.
Triodes and early amplifiers
At the beginning of the 20th century, the world experienced a rapid development of technology. Mechanical engineering, industry, energy developed. It was at this time that such a science as electronics was born. At first, it did not have a wide practical application, but after half a century this direction became the most important for human civilization. Everything that people use today would be impossible without the development of electronic technologies. An important breakthrough of that period was the invention of a device called the triode.
Firstthe model of this device was a glass lamp with three electrical contacts and was designed to change the input signal of an electric current. The change occurred by amplifying the input signal. Thus, the first electronic amplifier in history appeared, which at the dawn of the century made it possible to make a breakthrough in the communications industry - the first wireless telegraph was created.
General Principles
The basic principle of operation of absolutely any amplifier of electrical signals, regardless of its functional purpose, is due to the fact that with small changes in the values of electric current and / or voltage at the input of the amplifying circuit, there is a significant increase in these parameters at the output, which can be put into practice.
The main part of any amplifier is a device called a transistor. It consists of three separate semiconductor elements that have electrical contacts - a collector, base, emitter. When an alternating current flows through them, depending on its direction, the transistor amplifies or attenuates the power of the input signal.
Amplifier parameters
The most important characteristic of the amplifier is the gain, and it is equal to the ratio of the parameter value at the input to the value of the parameter at the output of the circuit. In fact, this indicator gives the main idea of the quality of the device and its capabilities. Another important parameter is the amplitude characteristic. In fact, this is a functional dependence of the amplitude of the output indicators oninput signal values. The importance of this parameter lies in the fact that this dependence is non-linear, which means that the circuit will react differently to different values of the signal at the input. The third important parameter of an electronic amplifier is the frequency response, which actually shows the dependence of the gain value on the frequency of the input signal. As it turns out in practice, at different frequencies of the alternating current, amplification occurs in different ways.
Classification
There are several signs by which certain types of amplifiers are distinguished. The first is frequency. Low-frequency devices are capable of increasing the rate by no more than a hundred kilohertz. At high frequencies, it grows in the range from 100 kHz to 100 MHz, sometimes a little more. There are also so-called "selective" devices operating in a certain small frequency range. The fourth type of devices has the widest coverage. Broadband capable of amplifying from 10 Hz to 100 MHz.
Another typology is related to the fact that devices contain an active element. It can be, for example, a transistor. Allocate semiconductor, microwave amplifiers, diode, tube.
One of the newest varieties is parametric, where the increase in signal power occurs through the energy of a generating external source. The capacitance of a non-linear inductive element in an electrical circuit changes occasionally. There are tunnel diode amplifying devices that are used to transmit sound in radio receivers.
Moreclassification by modes is known. They are denoted by capital letters of the Latin alphabet. Until the 60s of the last century, there were only four classes: A, B, C, D. Subsequently, technologies improved and became more complicated, additional types of modes, subclasses, variable voltage amplifiers appeared.
Broadcast basics
The most important negative factor affecting the quality of a TV signal is the distance from the source (TV tower). If the distance from the TV tower is so high that the antenna is simply unable to catch the signal, it makes sense to include a TV amplifier in the network.
A television signal is a complex electromagnetic impulse that carries video and audio information. Because of this, amplifiers for TV antennas differ markedly from radio devices. There are many TV amplifiers, different in characteristics and functionality.
They are mainly divided into two categories - analog signal and digital TV amplifiers (DVB-T2). It is also worth taking into account that the choice of device depends on how many TV receivers you need to transmit the signal to.
Mobile Applications
The most important device for a person today is, of course, a mobile phone. Today, there are several billion handheld communication devices in the world. But what would be the use of them if there were no mobile networks? The phone turns into just an expensive toy when the subscriber is in places where there is no coverage of mobile signals. Every mobile devicethere is a link amplifier. The fact is that one built-in antenna for receiving a signal from a cellular operator will not be enough due to the fact that the signal weakens with distance from the source.
In order for communication to take place without interference, a special communication amplifier in the phone increases the power of the signal caught by the antenna and translates it into a form convenient for the subscriber. But sometimes even this built-in amplifier is not enough when the terrain coverage is too weak. And then special external amplifiers are used - repeaters that go separately from the phone kit.
Wi-Fi Application
In today's information age, it's hard to imagine your life without access to the World Wide Web. The most popular type of wireless connection is undoubtedly Wi-Fi. However, this technology has a noticeable disadvantage - a limited range. In the absence of obstacles, devices can receive the network at a distance of only up to 100 meters. This is not always convenient, especially for large companies or firms whose branches are located in different parts of the city.
WiFi amplifiers remove this disadvantage. These are special repeater devices that receive a weak electromagnetic signal, convert it into a stronger one and relay it to nearby Internet signal receivers. WiFi boosters are becoming more and more popular in the countryside, making this type of internet connection as popular as a mobile one.
Changing the audio frequency
A person is able to hear sound only within certain limitsperception. In fact, people cannot respond to sound signals with a frequency of more than 20 thousand Hz. Ultrasonic waves are heard only by some species of animals, predominantly nocturnal. As for the low-frequency ones, here the threshold for a person is from 16 Hz. Anything lower is called infrasound. Similar waves are formed when a meteorite falls, during storms. But such signals are inaudible to the human ear.
The frequency amplifier is used in many household appliances and appliances. These are TVs, radio transmitters, music centers. There are also separate special devices. Their essence is to achieve a certain frequency range, equal to what the human brain is able to perceive. Low frequencies are converted, the power of oscillations changes. In some devices, it is possible to adjust the timbres, the volume level. With the built-in equalizer, you can even adjust the amplitude of the signal.
Using radio tubes
Vacuum tubes are used in tube amplifiers. Such devices are popular in recording and music reproduction studios. Their advantage is that in addition to obtaining suitable frequencies, it is possible to obtain additional tones. They are called harmonics, and if in semiconductor devices they are both even and odd, then in tube devices - mainly only the first ones. The sound is clearer, the music is better.
The power of tube amplifiers is lower than in transistor ones, but their circuits are much simpler, without an abundance of complex parts. It is believed that such devices are more natur altransmit sound, especially high frequency ranges. Bass reproduction may be a problem. Therefore, it is recommended to listen to mainly vocal or jazz music using devices.
About monoblocks
There is a variety of electronic amplifiers, which are called monoblock. Their influence extends only to one sound channel. Hence the term, where "mono" means "single". Similar units were used by musicians from fairly well-known bands such as the Grateful Dead. Amplifiers run on tubes, but there are also transistors. Their advantage: they give excellent sound quality.
For stereo system equipment, two monoblocks are required. This is due to the influence on the right or left sound channel. In addition, it is desirable to purchase a pre-amplifier. Monoblocks are time-tested devices. They appeared among the first of their kind and are common to this day. Disadvantages - a rather high price and special requirements for placement and use. Therefore, only professional musicians who have the means can afford to equip such an audio system.
