That would take some time to explain so I'll just give you a link.
http://www.bcae1.com/ampclass.htm
"What is class AB push pull amplifier and give its circuit and description .?"
No, a push-pull amplifier can be built class A, class AB, class B, or class C depending on application.class A push-pull is used for low power audio usuallyclass AB push-pull is used for high power audio usuallyclass B and class C push-pull is used for very high power radio usually (B is typical for AM and C is typical for FM)
Class B operated amplifier is used extensively for audio amplifiers that require high power outputs. Its also used as the driver and power amplifier stages of transmitters.
When we get amplifier output current for 180 degrees of input. then it's called B class amplifier. In a push pull class B amplifier one of the two power transistors or other amplifying elements handles the positive half of the waveform and the other element handles the negative half of the waveform. In practice, push pull audio amplifiers are usually class AB; each power transistor handles slightly more than 180 degrees of input. This minimizes distortion (crossover distortion) when one of the two transistors ceases output and the other takes over.
When we get amplifier output current for 180 degrees of input. then it's called B class amplifier. In a push pull class B amplifier one of the two power transistors or other amplifying elements handles the positive half of the waveform and the other element handles the negative half of the waveform. In practice, push pull audio amplifiers are usually class AB; each power transistor handles slightly more than 180 degrees of input. This minimizes distortion (crossover distortion) when one of the two transistors ceases output and the other takes over.
Class C because of its high power gain.
low power linear amplifiers
A class AB amplifier of the complementary transistor type has two transistors in series. Both transistors can change the resistance. If the upper transistor, a npn type, has minimum resistance and the lower transistor, a pnp type, has maximum resistance, the output voltage is near the supply voltage. One transistor is totally open and has zero current, the other transistor is totally closed and has zero voltage. Working together both transistors can set the output to any voltage between 0 and supply voltage. The class AB efficiency maximum is 100% minus the bias-power, see for example D. M. Snider, "A Theoretical Analysis and Experimental Confirmation of the Optimally Loaded and Overdriven RF Power Amplifier", 1966. Today the overdriven class AB amps are called class D.
A: class a
high efficiency nearly with my practical 72%..and the cross over distortion had been eleminated by the slight shift of q point above cut off region Class AB push pull is used in battery powered amplifiers as used in radios because the current drawn reduces during quiet periods, saving battery power.
Class C amplifier.. A class D amplifier is more efficient than class B, and is more efficient than class C as well.
The main advantage is lower power dissipation as the amplifier is not conducting half the time, however the resulting disadvantage is that it is nonlinear unless the more complex push-pull amplifier design is used (requiring about twice as many components).