An Introduction to Digital Electronics

Ever wondered what the term digital really means? Literally, digital means 'relating to digits or fingers'. In other words, something that is countable. The signals we come across in nature are continuous in nature. By continuous I mean that they vary continuously in both time and amplitude. For example, take the case of your voice signal. As you speak, it produces a continuous variation, maybe in its amplitude or frequency with respect to time. Such signals are called analog signals. The following is an example of a typical analog signal.

Do you think this signal is countable? Yes, maybe in terms of peak amplitude or frequency, but will you be able to measure accurately the amplitude of the signal at any given time? Even the variation in time is infinitesimally small, which is not possible to measure or count. As a result, we get infinite number of  amplitude levels possible and infinite number of time durations. Thus, the signal is not countable.

So, how can we make this signal countable? We do this by measuring the signal at specific intervals in time, say after 1 second duration. This leads to discretization in time. What about the amplitude? That can also be discritized or divided into levels. For example, any amplitude between 0 and 0.9 Volts may be treated as 0 Volts, considering the signal is a voltage signal. The resulting signal may be as follows:

Here, we have discretized in time taking each sample after 3 seconds. The first diagram shows the signal discretized in amplitude, each amplitude level differing by one unit. The second diagram shows a discrete signal, that is the signal discretized in time. These two together result in a digital signal, as shown in the third figure, since at every point, its amplitude and time can be measured with 100% accuracy.

So, now that we have got a more clear idea of what a digital signal is, let us see what digital electronics deals with. Well, obviously digital signals. Digital systems are systems that can work on digital signals and transform them for various purposes according to our needs. However, I said a little while ago that most of the signals we come across in nature are analog signals. Then why do we need digital signals? It is due to the fact, that digital systems such as our computers can deal only with the digital signals. Digital electronics grew in demand due to the fact that the digital systems can be implemented very easily, using only switches. In the present day market, switches are implemented using transistors, thus making a system able to incorporate a huge number of switches as well as increasing the speed of operation of systems manifold. Digital systems ensure better security and less noise on transmission. Due to all these factors, digital electronics has become a very important and fast developing branch of electronics.

Having said so, we will next concentrate on how an analog signal may be converted into a digital signal in my next post.

As for the question I asked you in my last post,

"Why do we need a usb programmer rather than serial programmer on laptops?"

think a little more. I'll give you the answer on my next post. Till then, happy electronizing!