An amplifier is an electronic device that is designed to increase the power, voltage, or current of an electrical signal. It takes an input signal and produces a larger, more powerful output signal that has a higher voltage or current level.
The purpose of an amplifier is to increase the strength or amplitude of a signal so that it can be transmitted over longer distances, or to provide enough power to drive a load such as a speaker or motor.
Features of Amplifier
- High Gain
- Bandwidth
- Input and output impedance
- Distortion
- Noise
- Power supply
- Protection circuitry
Classification of Amplifier
Amplifiers can be classified into different categories based on various parameters. Some of the common classifications of amplifiers are:
1. Based on Amplification
Amplifiers can be classified into linear and nonlinear amplifiers.
Linear amplifiers – They provide a proportional output to the input signal.
Nonlinear amplifiers – They provide a non-proportional output to the input signal.
2. Based on Frequency Range
Amplifiers can be classified into wideband and narrowband amplifiers.
Wide band amplifiers – They provide amplification over a wide range of frequencies.
Narrow band amplifiers – They amplify only a small range of frequencies.
3. Based on Type of Output
Amplifiers can be classified into voltage and power amplifiers.
Voltage amplifiers – They provide an amplified voltage output.
Power amplifiers – They provide an amplified power output to drive a load.
4. Based on Input Signal
Amplifiers can be classified into AC-coupled and DC-coupled amplifiers.
AC-coupled amplifiers – They amplify only the AC components of the input signal.
DC-coupled amplifiers – They amplify both the AC and DC components of the input signal.
5. Based on Configuration
Amplifiers can be classified into single-stage and multistage amplifiers.
Single-stage amplifiers – They have only one amplifying device.
Multistage amplifiers – They have two or more amplifying devices connected in series.
6. Based on Amplifier Configuration
Amplifiers can be classified into Common-Emitter, Common-Base and Common-Collector Amplifiers
Common-Emitter Amplifiers – These amplifiers are commonly used in transistor-based amplifiers and provide high voltage gain.
Common-Base Amplifiers – These amplifiers have a low input impedance and are used in high-frequency applications.
Common-Collector Amplifiers – These amplifiers have a high input impedance and a low output impedance, and are used in voltage amplification applications.
7. Based on Biasing
Amplifiers can be classified into Class A, Class B, Class AB, and Class C amplifiers.
Class A amplifiers – They are biased to operate in the linear region and provide low distortion.
Class B amplifier – They are biased to operate in the nonlinear region and provide higher efficiency.
Class AB amplifiers – They are biased to operate in the nonlinear region and provide higher efficiency and lower distortion.
8. Based on Technology
Amplifiers can be classified into vacuum tube and solid-state amplifiers.
Vacuum tube amplifiers – They use vacuum tubes as the amplifying devices.
Solid-state amplifiers – They use transistors or integrated circuits as the amplifying devices.
Applications
- Audio Systems
- RF Applications
- Power Supplies
- Signal Processing
- Industrial Applications
- Scientific Research
- Instrumentation