Question
Download Solution PDFThe theoretical limit for the efficiency of class B amplifiers is ______.
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDF- Class B push-pull amplifier employs two identical transistors with input signals applied to two stages that are 180° apart from each other.
- The transistor to be operated in class B mode is kept at the cut off bias and current in this state will be equal to zero.
- The maximum efficiency of the class B amplifier is 78.5%.
Derivation:
The input and output waveforms during the class B operation.
The power efficiency of class B amplifier:
For the half-sine loop, Idc is
The output of IC is from 0 to π and π to 2 π it is zero
Idc = ( IC (max) ) / π
Therefore input power Pin for the input voltage of transistor VCC is
Pin =
Here factor 2 is introduced as there are two transistors in the push-pull amplifier.
R.M.S. value of collector current = ( IC )max / √2
R.M.S. value of output voltage = ( VCC )max / √2
Output power Po is
Po =
Overall efficiency η = [( Po ) / ( Pin )] × 100 = 25 π = 78.5%
The maximum conversion efficiency of a class B push-pull amplifier is 78.5%
Last updated on May 8, 2025
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