Class B amplifier is a type of power amplifier where the active device (transistor) conducts only for half cycle obey input signal. That means the conduction angle is 180 degree for a class B amplifier. Since the active device is switched off for half the input cycle, the active device dissipates less power hence the efficiency is improved. 78.5% is the theoretical maximum efficiency of Class B power amplifier. the schematic of a
From the above
Class B power amplifier output characteristics:
One way to realize a practical Class B amplifier is to use a pair of active devices (transistors) arranged in push-pull mode where transistor conduct one cycle and another amplifier conduct another half cycle. The output from both transistors are then combined together get a scaled replica of the input. Transformer coupling is solution for this problem and such amplifiers are called class B amplifier.
Advantages of Class B amplifies-
- High efficiency. when compared to the Class. A configuration.
- Push-pull mechanism avoids even harmonics.
- No DC components in the output (in deal case)
Disadvantages of Class B amplifier-
- The major disadvantage is the cross-over distortion.
- Coupling transformers increases the cost and size. It is difficult to find ideal Transformer.
- Transformer coupling causes hum in output and also effect the law frequency response.
Transformer coupling is not practically in case of huge loads.
Also Read- Frequency response of OP-AMP