3.1 DIGITAL ELECTRONICS ANALOGUE vs DIGITAL Signals Analogue and digital signals are used to transmit information such as audio or video into electric signals. In , information is translated into electric pulses of varying amplitude. In , translation of information is into binary format (zero or one), where each bit is representative of two distinct amplitudes. Digital circuits are preferred because of the with which their output can be manipulated by computers and because digital signals are less subject to transmission errors, more immune to noise and because they can be stored and manipulated without degradation. analogue technology digital technology ease Key differences Analogue signal Digital signal It is a continuous signal. It is a time-separated signal. It uses a continuous range of values. It uses the values 0 and 1. discrete It is represented by a sine-wave. It is represented by a square wave. It varies constantly from instant to instant. It exists only at one of a of levels. set The bandwidth of the analogue signal is low. The bandwidth of the digital signal is high. It is suited for audio and video transmission. It is suited to computing and digital electronics. Computers and digital signals As computers are made up of digital electronics, internally they respond to two kinds of electrical states: "on" or "off": these two conditions are represented by the two numbers: 0 and 1. The "on" position corresponds to a 1, and the "off" position to a 0. Therefore, computers use binary numbers, called or (short for binary digit) in place of decimal digits. binary digits bits Logic gates Most electronic devices perform operations by passing data through a number of which operate as electronic that react in one of the two ways of the binary code to the data put into it. There are three basic logic gates: AND, OR, NOT. The simplest possible gate is called an "inverter," or a NOT gate. It has an input, and the output is its opposite: if the input is 1, the output is 0 and vice versa. An AND gate is a circuit with two inputs and an output which is set to 1 only if both the inputs are 1. An OR gate is set to 1 if at least one input is one and 0 if both the inputs are 0. Other logic gates are: NAND, NOR, XOR and XNOR, which are combinations of the previous logic gates. logic gates 1 switches MORE Most logic gates have two inputs and one output. The input and the output signals of a gate can be in one of the two binary conditions: low (0) or high (1). The value of the output depends on the values of its inputs. The gives a list of all the possible combinations of inputs and the resulting output. 1 truth table
