Analogue And Digital Electronics – We can divide electronics into two main branches: one is analogue and the other is digital.
Those quantities whose values vary continuously or remain constant are known as analogue quantities. For example, the temperature of air varies continuously during 24 hours of a day. If we plot a graph between time and temperature recorded at different times, we get a graph as shown in Fig. 19.1. This graph shows that the temperature varies continuously with time. Therefore temperature is an analogue quantity. Similarly time, pressure, distance etc., are analogue quantities.
The part of electronics consisting of such circuits which processes analogue quantities is called analogue electronics. For example the public address system shown in Fig. 19.2 is an analogue system in which the microphone converts sound into a continuously varying electric potential. This potential is an analogue signal which is fed to an amplifier (Fig. 19.2). Amplifier is an analogue circuit which amplifiers the signal without changing its shape to such an extent that it can operate a loudspeaker. In this way loud sound is produced out of the speaker.
Now we take up digital electronics. The computer operates by counting the digits. The word digit has adopted from this mode of computer’s operation. that part of electronics which provides the data in form of a maximum and minimum voltage signals i.e. by two voltage levels only, is known as digital electronics. In contrast to analogue signal Fig.19.3 (b) shows a digital signal.
It can be seen that it has no continuous variations. For quite a long period the use of digital electronics was limited to computers only but now-a-days its application is very wide spread. Modern telephone system, radar system naval and other systems of military importance, devices to control the operation of industrial machines, medical equipments and many household appliances are all using digital technology.
In our daily life, the quantities that we perceive by our senses are usually analogue quantities which cannot be processed by digital circuits. To resolve this difficulty, a circuit has been designed which converts the analogue signal into a digital one in the form of digits. This circuit is known as analogue to digital convertor, i.e., ADC.
When we get analogue signal in the form of digital, then we can process it with digital circuit, the output of which is also in digital form. This digital output is converted into analogue form by a circuit known as digital to analogue convertor (DAC). As the output of DAC is an analogue signal, it can be readily sensed by us. Thus electronic systems used at present consist of both analogue and digital type circuits.