Class B push-pull (Transformer coupled)

Class B push-pull (Transformer coupled)

In normal class B amplifier output current flows only for one half cycle i.e conduction angle is 180° to ensure 360° operation class B push-pull is used

$Q_1$ conducts during positive half cycle of input ,so $I_{c1}$ flows
During negative half cycle of input ,$Q_2$ conduct $I_{c2}$ flows.these 2 current are combined at output
Eficiency
$V_{pp}=2V_{cc}$

$I_{pp}=\frac{2V_{cc}}{R^{,}_{L}}$ 
This circuit resembles action of a fullwave rectifier therfore
$I_c=\frac{2I_{m}}{Π}=\frac{2V_{cc}}{ΠR^{,}_{L}}$

$η =\frac{V_{pp}I_{pp}}{8V_{cc}I_c}$

$=\frac{2V_{cc}\frac{2V_{cc}}{R^{,}_{L}}}{8V_{cc}\frac{2V_{cc}}{ΠR^{,}_{L}}}=\frac{Π}{4}$=78.5%