How Does a Class AB Power Amplifier Reduce Crossover Distortion?

[lownavin]

I need to know how does it operate. The textbook that we got doesn't state clearly.
Can anyone guide me on how a class AB power amp work stage by stage ? Thanks in advance.

 

[rbj]

it's like a Class B push-pull amp (where one transistor is "off" whenever the other is "on"). but the Class B has a little problem of crossover distortion around zero (when both transistors are "off").

the Class AB biases the two push-pull so that they both are hanging on the threshold of "on" when the input signal is zero. this reduces crossover distortion.