An audio amplifier is an amplifier that adds a smaller audio signal while maintaining the smaller details of the smaller signal. The demands of today's audio industry have improved the architecture of audio amplifiers. The types of audio amplifiers available on the market and the specifications associated with them can help make the best choice for an audio amplifier integrated circuit for a specific application.

introduce
    An audio amplifier increases the amplitude of a small signal to a useful level while always maintaining the details of the small signal. This is called linearity. The more linear the amplifier, the more truly the output signal represents the input.
    As the audio market's amplifier performance requirements continue to change, audio amplifier topologies have made many advances. Therefore, designers must know the types of audio amplifiers available and the characteristics associated with each amplifier. This is the only way to ensure that you choose the best audio amplifier for your application. In this tutorial, we will examine the most important characteristics of each audio amplifier available today: Class A, Class B, Class AB, Class D, Class G, Class DG, and Class H.

Class A amplifier
    The simplest type of audio amplifier is Class A. The output transistor (Figure 1) of A Class A amplifier is on (that is, not completely turned off) independent of the output signal waveform. Class A is the most linear audio amplifier, but it is less efficient. Therefore, these amplifiers are used in applications that require high linearity and have sufficient power.
Class A audio amplifiers typically have higher linearity but lower efficiency

Class B amplifier
   Class B amplifiers use the push-pull amplifier topology. The output of a Class B amplifier contains a positive-negative transistor. To replicate the input, each transistor is only on in half (180°) of the signal waveform (Figure 2). This leaves the amplifier idle at zero current, resulting in increased efficiency compared to Class A amplifiers.
    Class B amplifiers require a trade-off: increased efficiency degrades audio quality. This happens because there is a crossing point at which the two transistors transition from the on-state to the off-state. Class B audio amplifiers are known to produce cross-distortion when dealing with low-level signals. They are not a good choice for low-power applications.
    With a Class B audio amplifier, the output transistor is only on during half (180°) of the signal waveform. To amplify the entire signal, two transistors are used, one conducting a positive output signal and the other conducting a negative output signal.
    This is a brief survey of the many types of audio amplifiers commonly used in design today. Obviously, when designing audio circuits for any type of device, care should be taken to determine the audio amplifier topology that is best suited for that application. A good understanding of these different categories of audio amplifiers will help you choose the best audio amplifier for your design.