Differentiate class A, Class B and class C power amplifiers.

Class A, Class B, and Class C Power Amplifiers:

Power amplifiers are electronic circuits that increase the power of a signal. They are used in various applications, including audio amplifiers, radio transmitters, and industrial control systems.

Power amplifiers are classified into three main types based on their operating characteristics:

1. Class A:

• In Class A amplifiers, the active device (usually a transistor) is biased so that it conducts current throughout the entire input signal cycle.
• This means that the transistor is always in the active region, which results in low distortion but also low efficiency.

Key characteristics of Class A amplifiers:

• High linearity
• Low distortion
• Low efficiency (typically around 20-30%)
• Suitable for low-power applications

2. Class B:

• In Class B amplifiers, the active devices are biased so that they conduct current for only half of the input signal cycle.
• This results in higher efficiency than Class A amplifiers, but it also introduces crossover distortion, which occurs at the point where one transistor turns off and the other turns on.

Key characteristics of Class B amplifiers:

• Higher efficiency (typically around 50-60%) compared to Class A
• Moderate linearity
• Crossover distortion
• Suitable for medium-power applications

3. Class C:

• In Class C amplifiers, the active devices are biased so that they conduct current for less than half of the input signal cycle.
• This results in even higher efficiency than Class B amplifiers, but it also introduces significant distortion.

Key characteristics of Class C amplifiers:

• Highest efficiency (typically around 70-80%) among the three classes
• Poor linearity
• High distortion
• Suitable for high-power applications where efficiency is more important than linearity

Comparison Table:

Characteristic	Class A	Class B	Class C
Bias	Always conducting	Conducts for half cycle	Conducts for less than half cycle
Efficiency	Low (20-30%)	Moderate (50-60%)	High (70-80%)
Linearity	High	Moderate	Poor
Distortion	Low	Crossover distortion	High
Suitable Applications	Low-power audio amplifiers	Radio transmitters, medium-power audio amplifiers	High-power transmitters, industrial control systems

In summary, Class A amplifiers offer the best linearity and lowest distortion, but they are inefficient. Class B amplifiers have higher efficiency and moderate linearity, while Class C amplifiers have the highest efficiency but also the highest distortion.

The choice of power amplifier class depends on the specific application requirements.