Differentiate class A, class B and class C amplifiers.

Class A Amplifiers:

• Definition: Class A amplifiers are a type of linear amplifier where the output signal is an amplified version of the input signal. This means that the output waveform follows the input waveform exactly.
• Operation: In a Class A amplifier, the transistor is always biased in the active region. This ensures that there is always current flowing through the transistor, even when there is no input signal. When an input signal is applied, the transistor's output current changes in proportion to the input signal.
• Advantages: Class A amplifiers offer excellent linearity and low distortion, making them ideal for applications where accurate reproduction of the input signal is critical. They also have a wide bandwidth and can amplify both small and large signals.
• Disadvantages: Class A amplifiers are less efficient than other classes of amplifiers, as they dissipate a significant amount of power as heat. This can lead to thermal issues and reliability problems.
• Applications: Class A amplifiers are commonly used in high-fidelity audio applications, where sound quality is paramount. They are also used in some radio frequency (RF) applications and instrumentation amplifiers.

Class B Amplifiers:

• Definition: Class B amplifiers are a type of nonlinear amplifier where the output signal is only produced during half of the input signal cycle. This means that the output waveform is a distorted version of the input waveform, with half of the waveform missing.
• Operation: In a Class B amplifier, two transistors are used in a push-pull configuration. One transistor is responsible for amplifying the positive half of the input signal, while the other transistor amplifies the negative half of the input signal. This results in an output signal that is missing half of the waveform.
• Advantages: Class B amplifiers are more efficient than Class A amplifiers, as they only dissipate power when the transistor is conducting. This results in lower power consumption and improved thermal performance.
• Disadvantages: Class B amplifiers have higher distortion than Class A amplifiers, as the output signal is distorted. They also have a narrower bandwidth and are not suitable for amplifying small signals.
• Applications: Class B amplifiers are commonly used in power amplifiers, where efficiency is more important than linearity. They are also used in some RF applications and switching power supplies.

Class C Amplifiers:

• Definition: Class C amplifiers are a type of nonlinear amplifier where the output signal is only produced during less than half of the input signal cycle. This means that the output waveform is highly distorted, with most of the waveform missing.
• Operation: In a Class C amplifier, the transistor is biased well into the cutoff region. This means that the transistor only conducts for a very short period of time, when the input signal is at its peak. This results in an output signal that is highly distorted, with most of the waveform missing.
• Advantages: Class C amplifiers are the most efficient type of amplifier, as they dissipate very little power. They also have a very wide bandwidth and can amplify very high frequencies.
• Disadvantages: Class C amplifiers have very high distortion and are not suitable for amplifying audio signals. They are also not suitable for amplifying small signals.
• Applications: Class C amplifiers are commonly used in RF power amplifiers, where efficiency is more important than linearity. They are also used in some switching power supplies and high-power transmitters.

Summary Table:

Class	Bias	Output Waveform	Efficiency	Linearity	Applications
Class A	Active	Follows input waveform	Low	Excellent	High-fidelity audio, RF applications, instrumentation amplifiers
Class B	Push-pull	Missing half of waveform	Medium	Good	Power amplifiers, RF applications, switching power supplies
Class C	Cutoff	Missing most of waveform	High	Poor	RF power amplifiers, switching power supplies, high-power transmitters