An Amplifier or Amp is an electronic device that is built to increase the power and stability of a signal (a time-varying voltage or current).
Amplifiers consists of a two-port electronic circuit that uses electric power from a power supply to increase the amplitude of a signal applied to its input terminals, producing a proportionally greater amplitude signal at its output.
Amplifier is the generic term used to describe a circuit that produces an increased version of its input signal.
Amplification is the method of enhancing the signal strength of any electronic device.
Almost all electronic equipment have some means of amplifying their own signals. The use of amplifiers can be found almost every where; in medical devices, scientific equipment, automation, military instruments, communication instruments, industries and even in home machineries.
In History, The first practical device that could do the work of amplification was the Triode Vacuum Tube, which was invented in the year 1906 by Lee De Forest, and later led to the first amplifiers in the year 1912. At that time, Vacuum tubes were used in almost all amplifiers up till the 1970s and later replaced by transistors. Today, most amplifiers use transistors, but vacuum tubes still continue to be used in some applications.
Amplifiers can be considered as a simple box or block that is consist of the amplifying device, such as a Bipolar Transistor, Field Effect Transistor or Operational Amplifier, which has two input terminals and two output terminals with the output signal which is much greater than that of the input signal as it has been "Amplified".
Amplifiers are used in various ways like in wireless communications and broadcasting, and in audio equipment of all kinds. They can be classified as weak-signal amplifiers and power amplifiers.
1. Weak-signal Amplifiers are used essentially in wireless receivers. They are also used in acoustic pickups, audiotape players, and compact disc players. A weak-signal amplifier is built to deal with exceedingly small input signals, in some cases measuring only a few nanovolts (units of 10–9 volt).
2. Power Amplifiers are used in wireless transmitters, broadcast transmitters, and hi-fi audio equipment. The most frequently-used device for power amplification is the bipolar transistor.
The Main function of an Amplifier is to turn a small electric current into a larger one, and there are various different ways to achieve this depending on exactly what you're trying to do.
To boost a significant constant electric voltage, an electromagnetic device called Transformer can be used.
Transformers are used in our daily household appliances and small devices with low voltage.
Transformers are widely used to drive low-voltage appliances such as MP3 players and laptop computers from higher-voltage household power outlets.
Transformers are also used in electricity substations to convert very high-voltage electricity from power plants to the much lower voltages that homes and offices require.
Electromagnetic Relay can be used to amplify an input current with a brief pulse of electricity designed to switch something on or off, you can use an electromagnetic relay to amplify it. A relay uses electromagnets to combine two electric circuits together so that when a small current flows through one of the circuits, a much larger current flows through the other. Using a relay, a tiny electric current can power something that would normally need a much larger current to operate it.
In the amplification of power, the two important things to consider are power output and efficiency.
1. Power output is usually measured in watts or kilowatts.
2. Efficiency is the ratio of signal power output to the total power input (wattage demanded of the power supply or battery).
The classification of an amplifier as either a voltage or a power amplifier is made by comparing the characteristics of the input and output signals by measuring the amount of time in relation to the input signal that the current flows in the output circuit.
Below are general and most common classes of amplifiers:
Class A Amplifier: Has a low efficiency of less than 40% however with good signal reproduction and linearity.
Class B Amplifier: This is twice as efficient as class A amplifiers with a maximum theoretical efficiency of about 70% because the amplifying device only conducts (and uses power) for half of the input signal.
Class AB Amplifier: Has an efficiency rating between that of Class A and Class B but poorer signal reproduction than Class A amplifiers.
Class C Amplifier: This is the most efficient amplifier class, however, the distortion is very high as only a small portion of the input signal is amplified therefore the output signal bears very little resemblance to the input signal. Class C amplifiers have the worst signal reproduction.
There are 3 major categories of amplifiers:
1. Voltage Amplifier
2. Current Amplifier
3. Power Amplifier
The available types of Amplifiers are:
1. Audio Frequency Amplifiers (A.F. Amplifiers): A.F. Amplifiers are used to supply audio frequency power for the loudspeakers.
2. Intermediate Frequency Amplifiers (I.F. Amplifiers): I.F Amplifiers are used in TVs, radios and radar broadcast.
3. Radio Frequency Amplifiers (R.F. Amplifiers): R.F Amplifiers are used to drive the radio antenna of a transmitter.
4. Ultrasonic Amplifiers: Ultrasonic amplifiers are responsible for ultrasonic wave amplification.
5. Wideband Amplifiers: Wideband amplifiers are used to amplify a band of frequencies. They are used to amplify from DC to several tens of MHz.
6. Direct Coupled Amplifiers (DC Amplifiers): Direct-coupled or DC amplifiers are used to further amplify the very low-frequency signals.
7. Video Amplifiers: Video amplifiers are used to improve video signals in order to display it in high-quality resolution.
8. Buffer Amplifiers: Buffer amplifiers are used for electrical impedance transformation from one circuit to another.
9. Operational Amplifiers: Operational amplifiers are used to perform mathematical operations on voltages.
10. Transistor Amplifiers: Transistor amplifiers are used to amplify the voltage or current of the input signal.
In the Full course, you will learn everything you need to know about Amplifiers with Diploma Certificate to showcase your knowledge/skill gained.
Amplifiers - Introduction
Amplifiers - Materials
Amplifiers - Transistors Overview
Amplifiers - Transistor Configurations
Amplifiers - Transistor Regions of Operation
Amplifiers - Transistor Load Line Analysis
Amplifiers - Operating Point
Amplifiers - Transistor as an Amplifier
Amplifiers - Transistor Biasing
Amplifiers - Methods of Transistor Biasing
Amplifiers - Bias Compensation
Amplifiers - Basic Amplifier
Amplifiers - Classification of Amplifiers
Amplifiers - Based on Configurations
Amplifiers - Multi-Stage Transistor Amplifier
Amplifiers - RC Coupling Amplifier
Amplifiers - Transformer Coupled Amplifier
Amplifiers - Direct Coupled Amplifier
Amplifiers - Power Amplifiers
Amplifiers - Classification of Power Amplifiers
Amplifiers - Class A Power Amplifiers
Amplifiers - Transformer Coupled Class A Power Amplifier
Amplifiers - Push-Pull Class A Power Amplifier
Amplifiers - Class B Power Amplifier
Amplifiers - Class AB and C Power Amplifiers
Amplifiers - Tuned Amplifiers
Amplifiers - Types of Tuned Amplifiers
Amplifiers - Feedback Amplifiers
Amplifiers - Negative Feedback Amplifiers
Amplifiers - Emitter Follower & Darlington Amplifier
Amplifiers - Noise in Amplifiers
Amplifiers - Video Lectures
Amplifiers - Exams and Certification
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