This document discusses class B power amplifiers, specifically class B push pull amplifiers. It describes the construction of a class B push pull amplifier using two identical transistors and two transformers. The input signals to the transistor bases are 180 degrees out of phase via transformer Tr1. During operation, either transistor T1 or T2 will be forward biased and conduct depending on the input signal polarity, while the other is reverse biased. This results in an amplified output signal. The efficiency of a class B push pull amplifier is calculated to be 78.5% due to both transistors conducting for only half of each input cycle. Advantages include high efficiency and distortion-free output, while disadvantages include using two bulky/expensive transformers and potential distortion