Explanation: The class B amplifier has zero DC bias as the transistors are biased at cut-off only. Each transistor conducts when the input is greater than the base-emitter voltage. The conduction angle is only 180° for this amplifier. They have higher efficiency than class A amplifiers.

Explanation: If Q-point is in cut-off, then IC varies only in the positive direction, for saturation, it varies in the negative direction. So the output of Class B amplifier is half sinusoidal. There is no effect in the shape or the frequency of the wave.

Explanation: To obtain sinusoidal output from a class B amplifier, two transistors must be used. Such a circuit is a class B push-pull amplifier, used in unturned power amplifiers and audio frequency power amplifiers.

Thus AC power = DC power/0.4 = 25/0.4 = 62.5 W.

Maximum efficiency occurs when VMIN=0 and efficiency is 78.5%.

Explanation: A class B amplifier helps increase efficiency, and the figure of merit reduces. The q power dissipation reduces and cross over distortion increases. Due to two transistors, when one transistor turns off the other does not begin conduction immediately, hence output current is zero for a short interval.

Due to this, even harmonics cancel out and decrease harmonic distortion. Thus output has half-wave symmetry.

Explanation: 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.

Explanation: The complementary symmetry push-pull amplifier uses one NPN and one PNP transistor to conduct in positive and negative cycles respectively. It does not affect efficiency or figure of merit, but since no transformer is being used, it is easier to fabricate on ICs.