Which of the following amplifiers operates in Class B mode?

The operation of Class B amplifiers is characterized by the use of two transistors that alternate in conducting the input signal. In this configuration, each transistor conducts for half of the waveform of the input signal, allowing for an efficient amplification with minimal crossover distortion between the two devices. This design leads to improved linearity and reduced power consumption when compared to other classes of amplification, such as Class A, which continuously conducts through the whole cycle.

In Class B operation, one transistor is active during the positive half of the waveform, while the other is active during the negative half. This alternation is vital for maintaining the fidelity of the amplified signal and enhancing thermal stability. The complementary arrangement of the two transistors also allows for an output stage that can handle greater power levels and improve the overall efficiency of the amplifier.

Other configurations or classes of amplifiers do not follow this alternation pattern. For instance, a Class A amplifier continuously conducts, regardless of the input signal, which leads to greater heat generation and reduced efficiency. Class C amplifiers operate with a conduction angle of less than 180 degrees, and can often be in cutoff for part of the signal cycle, whereas Class B specifically depends on the alternate conduction to work effectively.