Amplifiers

An amplifier is a device that utilizes a small amount of energy to produce and deliver a larger amount as the final output. An amplifier is characterized by various parameters like gain, output dynamic range, bandwidth and rise time, settling time and aberrations, slew rate, noise, efficiency and linearity. Depending on the application, there are many types of electronic amplifiers. Usually an amplifer is used in radio and television transmitters and receivers, microcomputers, high-fidelity ("hi-fi") stereo equipment and other electronic digital equipment as well as guitar and other instrument amplifiers. As per the conduction angle of the input signal through the amplifying device, the amplifiers can be classified as Class A, B, AB, C, D, among several other classes.

The Class A amplifier is a small signal linear amplifier. With this type of amplifier, the output devices are always placed near in the conduction region. They are more linear and less complex than other types. There are two output devices in the Class B amplifier and each of these conducts alternately for exactly 180 deg (or half cycle) of the input signal. Class AB amps have varying conduction angles from 180 degrees upwards, as chosen by the amplifier designer. The Class C range is popular for high power RF amplifiers and its efficiency is higher than that of A, AB, or B classes of amplification. Switching is used by Class D amplifiers to achieve high power efficiency. Class H and Class G amplifiers are marked by variation of the supply rails.