All About Amplifiers
Amplifiers are among the most commonly used electronic devices in the world. They serve as one of the basic building blocks of many circuits and come in a wide range of forms. Simply put, amplifiers are electronic devices that increase the power of a signal. In other words, they increase the amplitude of a signal, making it stronger than the given output. Though the operation of an amplifier is theoretically quite simple, there are a lot of factors they have to deal with. As such, there are many different types of amplifiers made for different applications. In this blog, we will discuss the many types of amplifiers and their unique characteristics.
The quality of an amplifier is determined by a series of specifications known as figures of merit. They are:
- Bandwidth: The frequency range in which the amplifier can operate.
- Noise: The amount of unwanted additional information included in the output.
- Skew Rate: The maximum rate of change of output.
- Gain: The ratio between the magnitudes of input and output. This is likely the most important factor to consider.
- Stability: The ability to provide reliable and constant output.
- Linearity: The degree of proportionality between input and output signals.
- Efficiency: The ratio between the output power and the power consumed. This is another critical characteristic.
- Output Dynamic Range: The ratio between the lowest and highest useful output levels.
Although amplifiers are sometimes classified based on their input and output parameters, there are four basic types: current amplifiers, voltage amplifiers, transconductance amplifiers, and transresistance amplifiers. Current amplifiers, as their name suggests, are a type of amplifier used to make a given input current higher. They are characterized by a low input impedance and high output impedance. A voltage amplifier amplifies a given voltage for a larger voltage output. These are characterized by high input impedance and low output impedance. Transconductance amplifiers change output current according to the changing input voltage, and transresistance amplifiers change output voltage according to the changing input current. These are also known as current-to-voltage converters.
Power amplifier is a general term that refers to the amount of power provided by the power supply circuit or the amount of power delivered to the load. Examples of power amplifiers include audio power amplifiers, servo motor controllers, push-pull amplifiers, and RF power amplifiers. Power amplifiers are typically found in the final output stages of a circuit. There are five classes of power amplifiers: Class A, B, AB, C, and D. Let’s take a look at the characteristics of each.
Class A power amplifiers’ characteristics include low signal distortion levels, simple design, constant conduction due to amplifying element bias, no charge storage problems, stability, and linearity, though they also have low efficiency and high heat output during operation. Class B power amplifiers have similar stability and reliability while being much more efficient and creating far less heat. Class AB power amplifiers combine the characteristics of the Class A and B characteristics and are the most common audio amplifier design. Class C power amplifiers are the least linear power amplifier and highest efficiency. They have high output distortion and low power dissipation. Finally, Class D power amplifiers offer the highest efficiency - theoretically 100%. They also have low power dissipation, low power consumption, and are more complex than other types of amplifiers.
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