What Is the Function of an Amplifier

What Is the Function of an Amplifier? A Complete Guide

When speaking to a large audience, using a loudspeaker alone is not enough to pass a message, so if you’re hosting a public gathering, chances are that you will need an amplifier.

An amplifier is a general term used to indicate any electronic device that can magnify a signal, current, power, or voltage. These devices are used mainly in communications and audio equipment. We will cover all you need to know about amplifiers and their role in this article.

How Does an Amplifier Work?

Amplifier technology started in 1906 with the triode vacuum tube, which later became the less bulky transistors around the 1960s.

These devices have an input and an output and need a power supply to work. They also rely on a current signal as input to produce a more significant output signal. In essence, an amplifier consists of a box with magnifying equipment consisting of a couple of input and output terminals. Examples of magnifying devices include a field-effect transistor, bipolar transistor, or operational amplifier.

In audio equipment, amplifiers take in these electrical signals carrying musical frequencies and magnify the output. When used with sound equipment, soundwaves convert sound signals into electrical signals, which then fluctuate when the sound wave compresses and refracts.

A recorder then translates the wave into a pattern in devices such as CD drives. When you play a song, the player converts these patterns into electrical signals and uses the electricity to move the speaker back and forth.

Categories of Amplifiers

You can categorize amplifiers depending on the type of signal they handle or based on their class.

Weak Signal Amplifiers

These amplifiers handlesmall input signals and are common in wireless receivers. They produce little distortion and internal noise and can increase the signal voltage multiple times. They’re commonly used in audio tape players, compact disc players, and acoustic pickups.

Operational Amplifiers

An operational amplifier is an integrated circuit with two input pins and an output pin. Its function is to amplify the voltage difference between the two input pins and produce the amplified signal.

An operational amplifier can be used in many ways, including performing multiple amplifications, especially when combined with an amplification circuit.

You can use an operational amplifier as a noise canceller. For instance, when using it for voice-related devices, you can use an operational amplifier to cancel certain frequencies and focus on a target frequency.

Power Amplifiers

Power amps mostly use vacuum tubes due to their superior output. They are standard in hi-fi audio equipment, wireless, and broadcast transmitters.

Power amplifiers affect the power output and efficiency of a signal, and can be categorized further into audio power amplifiers, RF power amplifiers, and DC power amplifiers:

Audio Power Amplifiers

These amplifiers magnify a weaker audio signal and are more common in speakers such as TVs and mobile phones. An audio power amplifier produces outputs ranging from a few to thousands of milliwatts, depending on the size of the audio device.

Radio Frequency Power Amplifiers

Radiofrequency power amplifiers propagate signals through wireless transmissions. The amplifiers use antennas to transmit these signals and may require a high voltage signal to work effectively. Radiofrequency power amplifiers can at times result in positive feedback and self-oscillations and may require neutralization.

DC Power Amplifiers

These work through Pulse Width Modulated (PWM) signals and are mostly used in heavy machinery. They consist of a microcontroller that increases its power and supplies it to DC motors and actuators.

Classes of Power Amplifiers

This classification depends on whether the output signal is linearly or non-linearly amplified.

What Is the Function of an Amplifier

Amplifiers range from Class A to D and differentiate between a linear or non-linear output signal. If the electronic amplifier produces an identical output signal, only larger, then this signal is linear. If the output is slightly distorted after going through the amplifier, this is a non-linear amplification.

Class-A Amplifiers

Class A amplifiers work overtime, and they’re still in action even when the signal is small or absent. These amplifiers are linear and ensure the quality of the output signal before releasing it.

For Class A amplifiers to work, the no-signal current has to be at least the same as the maximum load current. This is the least efficient class but still provides the least distorted output signals.

Class B Amplifiers

With this type of amplifier, the transistor operates on one-half cycle of the input signal. This way, it conducts at a 180-degree angle. It’s also more efficient than a class A because it loses less power as it operates. Despite their efficiency, you may experience more distortion with these power amplifiers.

Class-AB Amplifiers

Class AB amplifiers are a combination of both class A and class B. They are meant to leverage the advantages of both classes and overcome their challenges. Class AB has less distortion than Class B and is more efficient than class A.

Because this is a combination, AB amplifiers also consider the low current needs of class A amplifiers and the high current needs of class B amplifiers.

Class-C Amplifiers

Class-C amplifiers are non-linear and have a conduction angle of about 90 degrees. They are also more efficient than the previous ones, so there will be less heat production. Although they are superior in efficiency, Class-C amplifiers are primarily used in radio frequency oscillators.

Class-D Amplifiers

This is also called a digital amplifier or switching amplifier and is considered more efficient than the rest. Class-D amplifiers are also more compact and use switching techniques such aspulse width modulation. They are more common in compact audio power amplifiers in motor vehicles.

Factors that Promote Stable Amplifier Operations

Slew Rate

The slew rate is how fast your amplifier responds and its maximum voltage rise rate. Measuring this involves gauging the voltage change per second.

Frequency Band

The frequency band represents how fast your amplifier moves. Your amplifier should move at a speed that corresponds with the input speed. This way, the amplitude of the signal remains at an optimum.


Your amplifier may be operating at high speed, but your cabling may hinder how effectively it works. Issues such as capacitance also affect the rising speed of the voltage waveform. Longer cables have greater capacities, so musicians prefer low electrical resistance cables, shorter in length.


Other than the speed, an amplifier’s load matters when it comes to an amplifier functioning optimally.

First is the inductive load (lagging load), which are essentially inductive AC loads that show the voltage-current relationship. An alternating current’s delivery is delayed over an alternating voltage when current flows into an inductive load.

Next is the capacity load, which also shows an aspect of a voltage-current relationship. If you’re looking to operate at high speed under constant-voltage control, then you will need a large current. In relation to capacity load, you will need to understand the input and output characteristics of power supply before using it.

The third factor is the diode load which deals with current control. Your overvoltage protection device will react to any slight offset in output voltage and this may cause failure.

FAQs About Amplifiers

What is Amplification?

Amplification is the process of increasing the strength of an input signal so that it’s more perceivable. A power amplifier for instance, supplies power supply to output devices such as passive soundbars and speakers to make amplification possible.

What Is the Difference Between a Preamp and a Power Amp?

The difference between a preamp and a power amp lies in their locality: a preamp precedes a power amp.

A preamp produces a high amount of gain to boost a weak output signal to line level. This makes it easy for the power amplifier to boost the amplified signal to its intended level.

For instance, when using musical instruments, a preamp uses several settings to tune a power amp’s sound quality by manipulating controls such as gain, middle, bass, and treble. The power amp then boosts the overall sound before it hits the speakers.

What Factors Affect a Power Amp’s Performance?

A power amp’s performance is mostly affected by the resistance load of its speakers. Resistance load or impedance represents the load a speaker places on an amplifier.

Your amplifier supplies current to a speaker, which “resists” it. This resistance is measured in ohms (Ω).

Signals from an amplifier will carry different frequencies, and impedance follows the changes. Because of the constant frequency changes, speaker manufacturers can’t set an exact frequency, and they resort to calculating a sort of average impedance.

Typically, most manufacturers create speakers with nominal impedances ranging from 4ohms, 6ohms, 8ohms or 16ohms. Remember that a lower impedance makes for a better power amp.

What Should You Consider Before Getting an Amplifier?

Before deciding on an amplifier, consider important factors including power output, mechanism, and class. If you’re working with audio files, then consider whether the amplifier you choose can perform noise cancellation tasks.


This article shows that many factors go into an amplifier’s working mechanisms. There are many types of amplifiers, each with its own function and characteristics. We have also covered some of the factors that promote stable amplifier operations.

Now that you know more about what is the function of an amplifier, you are ready to pick the one for you!