Power Amplifier Classes A-B-AB-C

They are broadly classified into two categories. Power amplifiers designed to amplify analog signals are classified into categories A, B, AB or C. Power amplifiers designed to amplify pulse width modulated (PWM) digital signals are classified into D, E, F, etc. The most widely used power amplifiers are those used in audio amplifier circuits and are classified into classes A, B, AB or C.

Class A power amplifier

Analog waveforms are composed of positive highs and negative lows. In this class of amplifiers, the entire input waveform is used in the amplification process. Amplifiers are the most used type of power amplifiers.

The driving angle (the portion of the waveform used for amplification, 360°) for class A amplifiers is 360°.

Class B power amplifier

Class B Power Amplifiers: This class of amplifiers uses two complementary transistors. So each active device conducts half (180°) of the waveform and two of them, when combined, amplify the entire signal.

Class AB power amplifier

Class AB amplifiers are a combination of class A and class B amplifiers to reduce the problem of lower efficiency

Class C power amplifier

The design of class C power amplifiers allows for higher efficiencies but reduces the linearity/conduction angle, which is less than 90°.

Applications:

1. Consumer electronics

2. Wireless communication