In audio electronics, power amplifiers are alphabetical symbols applied to various amplifier classes. The first class gives a general idea of the characteristics and performance of an amplifier. The second class is characterized by a specification that specifies the power ratings in Watts (W). Amplifiers of this class are usually characterized by high power ratings. Amplifiers of the third class are used for high volume audio streams. The fourth class has no specific specification and is used for an unspecific combination of powers.
Class B: This amplifier type offers high efficiency with low distortion. On the other hand, it lacks the ability to produce a full 360 degree output signal. Class B amplifiers typically come in high-power variants. Class C: This class is a true multichannel amplifier. It enables input signals to be processed by more than one processor.
Class D: The class d amplifier operates between linear and angular phases. Linear amplifiers operate using a pair of transistors operating in a linear mode. Angular phase amplifiers use a single transistor operating in an angular phase. Multipolar amphetamines of this class use a pair of transistors in each of the left and right phase. These are biased in a manner that produces a symmetrical waveform.
Class E: This class is a bipolar non-linear amplifier. A pWM amplifier uses a non-linear control signal to modify the output signal. A lot of advantages offered by this class makes it very popular. The switching device can be any one of the five common types of semiconductor coupled devices such as anode, cathode, bipolar or gate oxide capacitors.
Class F: This class is also known as Constant Power Multiplier (CPMS) amplifier. The advantage of using this class of amp is the lower distortion levels observed. However, they are more expensive compared to the previous two classes of amp. CPMS utilize one transistor instead of two or more for each input source. The result is improved efficiency and better power rating than the Class B and Class C. They also have a higher than average RMS output signal.
The operation of Class F amplifiers is characterized by a variable smoothing curve with low slope. CPMS can operate on one of the following sources - constant current (CC), pulse width modulation (PWM), linearity, or output division multiplexer (ODM). The most commonly used output stages are linearity and ODM. There are other classes of alphabets that fall below these groups such as hybrid amplifiers where there are four different amp sources along with separate control circuits.
Get a general overview of the topic here: https://en.wikipedia.org/wiki/Amplifier_(disambiguation).
