Electronics Engineering » Notes » Single Stage Transistor Amplifiers 1. There are four classes of amplifier operations : Class A, Class AB, Class B, and Class C. 2. Class A amplifiers operate entirely in the active region and thus the output if a faithful reproduction of the input signal with some amplification. In a Class A amplifier the efficiency is very low. Class A amplifiers are usedfor audio and frequency amplification. 3. Class AB amplifiers are biased so that the collector current is cutoff for a portion of one cycle of the input and so the efficiency is higher than that of a Class A amplifier. Class AB amplifiers are normally used as push−pull amplifiers to alleviate the crossover distortion of Class B amplifiers. 4. Class B amplifiers are biased so that the collector current is cutoff during one−half of the input signal. Therefore, the efficiency in a Class B amplifier is higher than that of a Class AB amplifier. Class B amplifiers are used in amplifiers requiring high power output. 5. Class C amplifiers are biased so that the collector current flows for less than one−half cycle of the input signal. Class C amplifiers have the highest efficiency and are used for radio frequency amplification in transmitters. Figure-1 :…