Fundamental principles of amplification

Abstract

An amplifier consists of any system or device by means of which a small signal power can control a larger. Many different ways by which this effect can be achieved have been discovered, but not all of them have turned out to be practically useful. Five methods have, however, achieved widespread use and these will be described here. The development of electronic engineering sees the invention of many devices, having improved properties, which can be applied to one or other of these five common amplifier types, but the invention of entirely new methods of amplification is a much rarer event. Thus if the underlying principles explained in this chapter are properly understood they form a basis for an understanding of all existing amplifiers, which may easily be extended to include newly invented amplifying devices.