Transistors takes approximately 0.7 volts (measured from base to emitter) to start conducting. In a pure class B amplifier, the output transistors are not "pre-biased" to an "ON" state of operation.

This means that the part of the output waveform which falls below this 0.7 volt window will not be reproduced accurately as the transition between the two transistors (when they are switching over from one transistor to the other), the transistors do not stop or start conducting exactly at the zero crossover point even if they are specially matched pairs. The output transistors for each half of the waveform (positive and negative) will each have a 0.7 volt area in which they are not conducting. The result is that both transistors are turned "OFF" at exactly the same time.

Fig.1 Shows Input signal (Red wave form) and Output (Yellow Waveform)

Fig.2 Shows Input signal (Red wave form) and Output (Yellow Waveform)

Fig.3 Shows Input signal (Red wave form) and Output (Yellow Waveform)