What is the Difference Between an Analog and Digital System?

This classification is based upon the type of signals used in the systems. Before looking into the differences between an analog system and a digital system, let us first try to see what the terms analog and digital mean.

An Analog signal is one in which the values taken can be continuous. For example, if a signal varies in magnitude between 0 volts and 5 volts, it can take any value between 0 and 5.

With a digital signal, there can only be discrete values. For example, a signal ranging from 0 to 5 volts could take the discrete values of 0, 1, 2, 3, 4 and 5 in a digital system. If a signal in the above digital system has the value of say, 2.2 at any instant of time, it is represented by the nearest discrete value (2, in this case). It may be noted that all signals ranging from 2 to 2.5 would be represented by 2 and all signals ranging from 2.5 to 3 would be represented by 3.

As a special case, if a signal in a digital system is represented by only two values - zero or one, it is called a binary system and this is the representation used by all modern-day computers and communications.

The use of analog systems has been dwindling as implementing digital systems has become more cost-effective. Both systems have their advantages and disadvantages - Analog systems make efficient use of bandwidth and are relatively immune to noise. They are also less flexible to changes in design. Analog systems are implemented with hardware components and are not usually flexible to changes in parameters of input signals. Any change in input parameters may require a fresh circuit design and implementation.

Digital systems on the other hand, are greatly affected by noise. The advantage with digital systems is that they are built using programmable components and a standardized circuit can handle digital signals and a system can be implemented through software. This means that the components can be reused just by modifying the program.

Most modern communication systems are digital systems - any analog inputs are converted to digital by a process called sampling and conversion from digital back to analog is by reconstruction.