Crossover distortion is later explained in this article. Then this circuit is known as Class AB amplifier circuit. To overcome this problem, diodes are used for biasing, and then the amplifier is known as Class AB Amplifier.Ī common method to remove that crossover distortion in Class B amplifier is to bias both the transistor at a point slightly above then the cut-off point of transistor. Same thing happen with PNP transistor in negative half cycle of AC wave, this is called Dead Zone. So when AC input voltage is applied to push-pull amplifier, it starts increasing from 0 and until it reaches to 0.7v, transistor remains in OFF state and we don’t get any output. We know that, a transistor requires 0.7v at its base-emitter junction to turn it on.
Circuit diagram for Class B amplifier is given below:Ĭlass B generally suffers from an effect known as Crossover Distortion in which signal get distorted at 0V. One transistor pushes the output on positive half cycle and other pulls on negative half cycle, this is why it is known as Push-Pull Amplifier. Therefore, the conduction angle of this type of amplifier circuit is 180 Degree. The Class B amplifier circuit is biased in such a way that each transistor will work on one half cycle of the input waveform. Efficiency of Class B amplifier is higher than Class A amplifier, as it consists of two transistors NPN and PNP. The circuit diagram for Class A amplifier is given below:Ĭlass B amplifier is the actual Push-Pull Amplifier.
The stages of the Class A amplifier allows same amount of load current to flow through it even when there is not input signal connected, therefore large heatsinks are needed for the output transistors. The efficiency of Class A amplifier is very low near to 30%. It produces minimum distortion and maximum amplitude of output signal. It consists of only one switching transistor which is set to remain ON always. There are three classification of Push-Pull Amplifier but generally Class B Amplifier is considered as Push Pull Amplifier.Ĭlass A configuration is the most common power amplifier configuration. The advantage of Push-Pull amplifier is that there is no power dissipated in output transistor when signal is not present. It consists of two transistors in which one is NPN and another is PNP. Push-Pull Amplifier is a power amplifier which is used to supply high power to the load.
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