Question

Why does no DC current flow in the primary winding of the output transformer of class B push-pull amplifier?

(a) Because DC currents from both transistors flow in opposite directions

(b) Because the net impedance is very high to allow flow of current

(c) The winding only allows AC current to flow

(d) Current only flows in secondary winding due to the presence of load at that side

I had been asked this question in an online quiz.

The origin of the question is Push-Pull Class B Amplifier topic in section Power Amplifier of Analog Circuits

Answer 1

Correct option is (a) Because DC currents from both transistors flow in opposite directions

The best I can explain: The net DC current in the primary winding of the output transformer is zero because DC collector currents of both transistors being used flow in opposite directions and hence transformer saturation doesn’t occur.