Explanation: Class B amplifiers are characterized by each active device conducting for exactly 180 degrees of the input signal cycle. In a common push-pull configuration, one transistor handles the positive half of the waveform, conducting for 180 degrees, while a second transistor handles the negative half, also conducting for 180 degrees. This allows for higher efficiency compared to Class A by significantly reducing quiescent current. * **Class A** amplifiers conduct for the full 360 degrees of the input signal, providing excellent linearity but low efficiency. * **Class C** amplifiers conduct for *less* than 180 degrees (typically between 90 and 150 degrees), offering very high efficiency but significant distortion, making them suitable only for tuned RF circuits where a resonant tank can restore the original waveform. * **Class D** amplifiers are switching amplifiers that operate transistors in a fully on or fully off state using pulse width modulation (PWM), rather than a continuous conduction angle, achieving very high efficiency.