What Is An Amplifier And How It Works?

What is an Amplifier?

An electronic amplifier, amp, or amplifier is an electronic device that is capable of increasing the signal power which is a time-varying current or voltage. A two-port electronic circuit, an amplifier is known for utilizing the electric power from the supply to increase the signal’s amplification that is applied to the input terminals. At its output, it produces a proportionally greater amplitude signal.

The amplifier produces amplification which is measured by its gain; it is the ratio of output voltage, power, or current. An amplifier is known for possessing power gain which is greater than one. An amplifier is mainly an electrical circuit that is contained by another device or a separate piece of equipment. Amplification is considered essential for modern electronics as amplifiers are used in various electronic equipment.

The amplifier is a device in electronics that responds to various small input signals such as power, voltage, or current. It is known for delivering large output signals consisting of waveform features of the input signal. There are amplifiers of different types that are used in electronic equipment such as television receivers, radio, computers, and audio equipment with high-fidelity.

The amplifying action may be provided by various electromechanical devices including transformers, generators, and vacuum tubes. Mostly, the electronic systems employ solid-state microcircuits in the form of amplifiers. Generally, an integrated circuit comprises numerous transistors and devices which are related to it on a small single silicon chip.

It has been observed that a single amplifier is insufficient in raising the output as per requirements. In these types of cases, the first output is fed into the second one which is fed to the third, and so on. This process continues until the satisfactory output is received by the user. This results in a cascade or a multistage amplification. As you now know what is amplifier, it’s time to go through its uses.

Uses of Amplifier

Mostly, electric devices make use of amplifiers for providing different amounts of signal amplifications. Mostly, the signals are too small in size to drive or control the device of choice, this is where amplifiers are needed. Let’s understand this with the help of an example. The audio signal that is extracted from records is too small to drive a speaker.

In this condition, amplification is needed to complete the task. The signal is usually amplified numerous times in between the speaker and the record player’s needle. Every time the signal is amplified, it is required to pass through an amplification stage. An audio amplifier connected between a speaker system and a turntable generally comprises various amplification stages.

An amplifier also known as an operational amplifier is a circuit mostly used for controlling and automating electronic circuits in various marine applications. Generally, the applied input signal is a current or voltage signal. The aim of an amplifier is to deliver an output signal which is larger than the input signal.

The purpose of an amplifier or op-amp is to increase or amplify the input signal to deliver or produce an output signal. These signals are usually larger than the input signals but have a waveform that is similar to the input. Majorly, the change in the output signal is denoted by the increase in the power level. D.C. voltage is known for supplying the additional power externally.

In an amplifier, the input signal controls the output signals. The compact and small-signal amplifiers in the electronic components are used as devices because of the ability to raise small input signals to a larger magnitude. After learning about what is amplifier and the uses of the amplifier, let’s read about the types of amplifiers.

Types of Amplifiers

On the basis of the property of output, amplifiers are divided into three categories. These categories include voltage amplifier, power amplifier, and current amplifier. Voltage amplifiers are the commonly used amplifiers in electronic devices. These amplifiers are known for increasing the amplitude of the signal’s output voltage.

Current amplifiers are the ones that increase the amplitude of the input current in comparison to the input current waveform. The power amplifiers are used for increasing the power which refers to the product of output current and voltage which is more than the product of input current and voltage.

The current or voltage at the output may be less than the input but the overall current or voltage product is more than the input. A part of the AC signal is amplified each time is applied to the amplifier. On the basis of the signals that are amplified by the amplifiers, they can be further divided into the following.

Audio Frequency Amplifiers

A.F. Amplifiers or audio frequency amplifiers are the ones that amplify the audio frequencies. These audio frequencies are generally in the range of 20 Hz to 20kHz among which some HI-FI amplifiers are capable of amplifying up to 100 kHz.

These are used for supplying the audio frequency power for operating the loudspeakers. Mostly, the modern audio amplifiers are based on some solid-state drives such as the transistors while in the early stages these are created out of the vacuum tubes.

Intermediate Frequency Amplifiers

I.F. Amplifiers or Intermediate Frequency Amplifiers are the ones that are amplified by the amplifier. These types of amplifiers are utilized in radio, radar, or television. They are known for providing the maximum voltage amplification of radio, television, or a radar signal. This happens before the audio or video information carried by the signals is demodulated.

The frequency of operation observed here is lower than the radio signal received. However, they are higher than the video or audio signals which are produced by the system in due course. Here, the frequency at which the I.F. amplifier has to operate is decided by the equipment.

Radio Frequency Amplifiers

R.F. amplifiers or radiofrequency amplifiers are known for increasing the power of radio signals with low frequency. These are specifically used for driving the antenna of a transmitter. These amplifiers are the tuned ones whose operating frequency is being controlled by the tuned circuit.

Under this, the circuit may be adjusted on the basis of the amplifier purpose. The input resistance and the gain found here is considerably low. These amplifiers have a special feature which is creating low noise during the performance. These are generally used in the early stages of the receiver.

It has been observed that the background noise produced by the electronic device is at a low value here. This happens because the amplifier is capable of handling very low amplitude signals from the antenna.

Ultrasonic Amplifiers

Ultrasonic amplifiers are the ones that amplify the ultrasonic waves. These are present in the frequency range lying between 20 kHz to 100 kHz. These are used for special purposes such as ultrasonic cleaning, ultrasonic scanning, remote control systems, etc. Each of these types is known for operating at a narrow band of frequencies lying within the ultrasonic range.

Wideband Amplifiers

These amplifiers are known for amplifying a band of frequencies. They are generally known for amplifying from direct current to numerous tens of MHz. These are used in various equipment such as oscilloscopes. They are used in areas where there is a requirement for accurate measuring signals spread across a wide range of frequencies. Their gain is low as a result of their wide bandwidth.

Direct Coupled Amplifiers

DC amplifiers or direct coupled amplifiers are the ones that are used to amplify the low-frequency signals. In these, the output of one stage is generally coupled with the input of the following stage in these amplifiers. These amplifiers are known for amplifying the direct current frequency which is zero. These are mostly utilized by numerous measuring instruments and electrical control systems.

Video Amplifiers

Video amplifiers are used for improving the quality of video signals and display the same in a higher resolution. The signals act as a medium for carrying the entire information about pictures in television and radar systems. These may be classified as a special type of wideband amplifier which is specifically used for sending signals that are applied to video equipment.

The usage of video amplifiers forms the basis for its bandwidth. In the case of the TV receivers, these are extended from 0Hz to 6MHz and wider in the case of radar. These amplifiers are utilized for the purpose of amplifying the signals that are received from computer monitors and DVDs. These may also be used for amplifying the video quality in televisions which are smaller in size and are installed in vehicles.

Buffer Amplifiers

Buffer amplifiers are generally used for transforming electrical impedance from one circuit to the other. These are known to have an amplifier gain of one. These are also used for the purpose of isolating circuits from each other. These are known to have a higher impedance level at the input and a lower impedance level at the output.

This is why these may be used as an impedance matching device which indicates that the signals are not attenuated between the circuits. This happens when a circuit having a high level of output impedance feeds signal directly to the other circuit which has a low level of impedance.

Operational Amplifiers

Operational amplifiers are basically amplifiers with high gain electronic voltage. These are used for performing various mathematical operations on voltages. Not only this, these are used in the form of ICs which were initially developed with vacuum tubes. The operational amplifiers are known for having two main input terminals.

These two terminals are inverting and non-inverting which may be used as inverting amplifiers, summing amplifiers, difference amplifiers, and non-inverting amplifiers.

Transistor Amplifiers

Transistors are electronic devices that are used as amplifiers. These are known for amplifying the current of the voltage of the input signal. Mainly there are two types of transistor devices which are BJT or Bipolar junction transistors and FET or Field effect transistors.

Transistor amplifiers are generally analyzed in various distinct configurations. These include a common emitter, common base, and common collector by using BJR. Under FET, these amplifiers are analyzed in the following configurations which are common gate, common source, and common drain.

A small current at the terminal base of the bipolar junction transistor may be useful in controlling the current at the collector, and emitter. In FET or field-effect transistors, a small voltage at the gate may control the voltage at the drain or at the source.

Classification of Amplifier Stages and Systems

An amplifier is known for its ability to strengthen the signal. Let’s read about the Classification of Amplifier Stages and Systems. On the basis of a number of stages, there are single-stage amplifiers and multi-stage amplifiers. The single-stage amplifiers are the ones that have a single transistor circuit which may be said to be a single-stage amplification. A multi-stage amplifier has multiple transistor circuits which are known for providing multi-stage amplification.

On the basis of output, amplifiers may be classified into power and voltage amplifiers. A voltage amplifier is one that is known for increasing the voltage level of the input signal. A power amplifier is the one in which the circuit is known for increasing the power level of the input signal.

On the basis of the magnitude of the input signal applied, the amplifiers may be classified as small signal and large signal amplifiers. A small-signal amplifier is the one in which the input signal is weak to be able to produce small fluctuations in the collector current in comparison to the quiescent value. An amplifier is termed as a large signal amplifier when the fluctuations in the collector current are large beyond the linear portion of the characteristics.

On the basis of the frequency range, amplifiers may be classified as audio and radio amplifiers. The amplifier’s circuit which is capable of amplifying the signals lying in the audio frequency range between 20 Hz to 20 kHz frequency range is termed an audio amplifier.

A power amplifier is the one that amplifies the signals that lie between a very high-frequency range.

On the basis of the coupling method, amplifiers are categorized as RC coupled, Transformer coupled, and direct-coupled amplifier. RC coupled amplifier is a multi-stage circuit that is coupled to the following stage by using a combination of capacitor and resistor. This is why it is termed an RC coupled amplifier.

A transformer-coupled amplifier is an amplifier which coupled to the next stage with the assistance of a transformer whereas a Direct-coupled amplifier is the one that is coupled to the next stage directly.

On the basis of transistor configuration, amplifiers may be divided into CE amplifier, CB amplifier, and CC amplifier. The amplifier which is created by using a CE configured transistor combination is termed a CE amplifier. The amplifiers which are created by using a CB configured transistor combination and a CC configured transistor combination are may be termed as CB amplifier and CC amplifier respectively.

Classes of Amplifier

As you have now read in detail about what is amplifier, its uses, and other details, let’s get to know about its classes as well. Amplifiers are classified into different classes on the basis of their operating characteristics and construction.

Amplifier classes are a term that is being used to refer to the differentiation between various types of amplifiers. These represent the amount of output signal which is known to vary within the amplifier circuit over a single cycle of operation when it receives a sinusoidal input signal.

Depending on the mode of operation amplifiers are classified into various classes such as Class A, Class B, Class C, and Class AB. In class A amplifier, the conditions are such that the collector current flows for the entire AC signal circuit which is being used. In class B, the collector current flows for only the half cycle of input.

Coming to class C, the collector current in this, flows for less than half of the cycle of input. Class AB amplifier is a combination of class A and class B which makes it accessible to the benefits of both the classes and reduces the problems. This was about the classes of amplifiers now let’s read about the functions of amplifiers.

Functions of Amplifier

The work of an amplifier is to convert a small electric current into a bigger one. There are numerous techniques that may be applied to achieve this. Power amplifiers are considered necessary as they have a variety of devices comprising microwave ovens, headphones, home theatre systems, etc. which are commonly used electronics.

The motors such as DC motors, servo motors, etc. are the ones that use amplifiers in order to increase the throughput of the running electric motors. Communication through long-distance has become possible by utilizing efficient power amplifiers. Higher is the rate of transfer, the more it is used in electronic applications.

How Does an Amplifier Work?

Understanding what is amplifier is not enough, you must also know how it works. In general language, the word amplifier is used for denoting stereo components but in reality, it is just a small representation of it.

We are surrounded by them in the form of computers, television, CD players, speakers, etc. The work of an amplifier is to generate a new output signal in exchange for an input signal. These may be imagined as two separate circuits, the output circuit, and the input circuit.

The output circuit is the one that is generated with the assistance of the amplifier’s power supply. This process draws energy from the battery or the power outlet. If the amplifier is powered by the AC current of the household where the direction of the charge flow changes, the power supply gets converted into direct current if the flow direction of charge is the same.

The input circuit is basically the electrical audio signal which is recorded on the tapes which run in from a microphone. A varying resistance is applied to the output circuit for re-creating voltage fluctuations of the audio signals which are original. This type of load is high in amplifiers for audio signals which are original.

Advantages of Amplifier

The advantages of amplifiers are numerous, let’s read about these. CE amplifier is a common emitter amplifier that is not only inverting but also has low input impedance. It has a high voltage gain, high output impedance, and high current gain.

A CB amplifier is considered a decent voltage amplifier with a current that is equal to the current out. Commonly, the base circuit is known to work best as a current buffer. It is capable of taking an input current at a low impedance and delivers a similar current to a higher impedance output.

The advantages of a CC amplifier consist of current gain while the voltage maintenance remains unchanged. It consists of the lowest output impedance in comparison to the other type of amplifiers. Also, it may be used for matching the impedance between the amplifier stage with low input impedance and the amplifier stage with high output impedance.

Disadvantages of Amplifier

The disadvantages of amplifiers are numerous, let’s read about these. The disadvantages of the CE amplifier are that it comprises high output resistance. It is known for providing a poor response to high frequencies. It has high thermal instabilities and the voltage gain is unstable.

The disadvantage of the CB amplifier is that it needs two DC power sources in order to run the circuit. It is known for measuring the voltage between the collector or output and the emitter and input. It compares voltage between the base and the emitter and maintains it within the limit of the transistor.

Hope now you have clearly understood what is amplifier, its uses, advantages, disadvantages, parts, classes, classifications, and types. An amplifier is an electrical circuit that is contained within the other device or a piece of equipment that is separate. Amplification is considered fundamental to modern electronics; in present times, these are used in various electronic equipment which we are surrounded by.

What is an Amplifier and How it Works?