This document provides an overview of amplifiers: 1. An amplifier is an electronic device that increases the magnitude of a signal applied to its input. Amplifiers are commonly used to amplify small input signals to drive speakers, lamps, or other loads. 2. Amplifiers can be classified by their configuration (common emitter, base, or collector), class of operation (A, B, C, or AB), and frequency of operation (DC, AF, RF, VHF, UHF, or SHF). Different types of amplifier gain include voltage, current, and power gain. 3. Power amplifiers are amplifiers that deliver relatively high power, usually to a low resistance