Introduction

‘Linear integrated circuits’ is the name given to ready-built, miniature amplifier circuits which can be used directly in a number of applications often with the addition of only a few passive external components. This contrasts with the approach described in the preceding chapters where active devices such as field-effect transistors and bipolar transistors were used together with a number of passive circuit components to form amplifier circuits. This latter approach has come to be known as discrete circuit technology, as opposed to the integrated circuit technology which we describe in this chapter. The technical advantages of integrated circuits, coupled with the convenience with which they may be used, are of such value that their use has become extremely widespread. Circuits using them are much smaller than those made with discrete components and today they are cheaper too. With integrated circuits, the basic building blocks of electronic circuits which used to be collections of separate devices such as transistors, diodes, resistors, etc. have been miniaturised into readybuilt circuits which can be easily linked together to form the desired system.

In most applications of integrated circuits a high gain amplifier forms the internal amplifier to which passive circuit elements are connected to provide an overall amplifier circuit called an ‘operational amplifier’. (Note that the terminology is sometimes confusing in that the internal amplifier is itself referred to as the operational amplifier.)