3 - Digital Circuits

Electrical signals in circuits is the basis for implementing binary based computing. The binary computation is implemented with the presence or the absence of a voltage in a given circuit. This two-state nature of on-off circuits is the same as the two state nature of binary and the two state nature of logic. The fact that all three areas have the same nature means that one can be represented in terms of the other. This fact allows logic and binary mathematics to be handled using electrical signals. This idea was first put forward by Claude Shannon in the 1930's (see history in chapter 1), and it led to the shift from mechanical computing devices to electrical computing devices. To understand the implementation of digital computing using circuits, a good understanding of circuit theory is needed. Circuits that are capable of performing calculations or calculation related functions using a two state voltage pattern are referred to as digital circuits. In this chapter we begin our study of digital circuits with an introduction to circuit theory, followed by a look at some of the circuit devices that are used to build digital circuits.