Amplifiers are devices that increase the power of an electrical signal. They are used in a wide variety of applications, including audio, radio, and telecommunications.
There are five main classes of amplifiers: class A, class B, class AB, class C, and class D. Each class of amplifier has its own advantages and disadvantages in terms of efficiency, linearity, and output power.
Class A Amplifiers
Class A amplifiers are the most linear of all the amplifier classes. This means that they produce the least amount of distortion in the output signal. However, class A amplifiers are also the least efficient. In theory, a class A amplifier can achieve 50% efficiency with inductive output coupling or 25% with capacitive coupling. However, in practice, the efficiency of class A amplifiers is typically much lower, often around 20%.
Class B Amplifiers
Class B amplifiers are more efficient than class A amplifiers, but they are also less linear. Class B amplifiers only conduct current for half of the input signal cycle. This means that they waste power during the other half of the cycle. In theory, a class B amplifier can achieve 78.5% efficiency. However, in practice, the efficiency of class B amplifiers is typically around 60%.
Class AB Amplifiers
Class AB amplifiers are a compromise between class A and class B amplifiers. They are more linear than class B amplifiers, but they are also more efficient. Class AB amplifiers conduct current for more than half of the input signal cycle, but not for the entire cycle. This results in a higher efficiency than class B amplifiers, but still less than class A amplifiers. In theory, a class AB amplifier can achieve 78.5% efficiency. However, in practice, the efficiency of class AB amplifiers is typically around 70%.
Class C Amplifiers
Class C amplifiers are the most efficient of all the amplifier classes. They only conduct current during a small portion of the input signal cycle. This results in a very high efficiency, often over 90%. However, class C amplifiers are also the least linear of all the amplifier classes. This means that they produce a lot of distortion in the output signal.
Class D Amplifiers
Class D amplifiers are the most efficient amplifier class for digital signals. They use a switching technique to amplify the signal. This results in a very high efficiency, often over 90%. Class D amplifiers are also very linear, making them suitable for audio applications.
Which Class of Amplifier Has the Lowest Efficiency?
The class of amplifier with the lowest efficiency is class A. Class A amplifiers are the most linear of all the amplifier classes, but they are also the least efficient. In theory, a class A amplifier can achieve 50% efficiency with inductive output coupling or 25% with capacitive coupling. However, in practice, the efficiency of class A amplifiers is typically much lower, often around 20%.
The efficiency of an amplifier is important for a number of reasons. A more efficient amplifier will consume less power, which can save money on operating costs. It will also generate less heat, which can be important for applications where heat dissipation is a concern. Finally, a more efficient amplifier will be able to amplify a signal for a longer period of time before it overheats.
The class of amplifier with the lowest efficiency is class A. Class A amplifiers are the most linear of all the amplifier classes, but they are also the least efficient. If efficiency is the most important factor for your application, then you should choose a class B, class AB, or class D amplifier.
