• As its name suggest class AB amplifier is the combination of class A and class B amplifier. The class AB is one of most widely used class of power amplifier to be used for design. The class AB amplifier is used to eliminate the cross over distortion in class B and to get more efficiency than class A.

• A power amplifier is referred to as class AB amplifier if the output signal is obtained for more than 180 degree and less than 360 degree. For class AB power amplifier the position of Q- point is just above cutoff region. Thus in absence of ac input signal the transistor is just conducting.

• A small bias voltage given using diode D1 and D2 as shown in the figure, which helps the operating point to be above cutoff region. The output waveform of class AB amplifier is as shown in the figure.

• Class AB amplifiers are called as linear amplifiers as the output signal amplitude and phase are same with input.

Advantages:

• The biggest advantage of class AB is it eliminates crossover distortion.

• This amplifier is preferred for audio system ,radio and TV receivers.

Efficiency:

• The efficiency of class AB is less as class B i.e than 78.5%

Applications:

• AF amplifiers in TV

• Public address system.