ABSTRACT

This chapter introduces amplifier equivalent circuits suitable for a.c. circuit analysis. It provides details of the specification of an integrated-circuit op amp. The chapter explains and analyses the effects of applying different types of feedback to op amps. Amplifiers are used to increase the power in the signal from a microphone so that it can drive a loudspeaker, or to amplify the control signals produced by the pilot of an aircraft so that they will move the flaps on the wings and other control devices. The extra power must come from a power supply. A very important type of amplifier, judging by how widely it is used, is the operational amplifier. It differs from the kind of amplifier discussed so far in that it has a differential input and that its output is always centred around zero volts. It is represented in diagrams by the triangular symbol.