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Only a few years ago, you would not have found the study of 'electronics' on the curriculum of any university or college. The subject was not considered important enough to be given a category of its own, and was studied as a rather specialist branch of electricity. Today, this relatively new branch of technology has made an impact on almost every aspect of our lives. Electronics has made possible a range of inventions, from televisions to spacecraft. Many of these inventions--or the effects of them have revolutionized the way we live.
The growth of electronics as a branch of technology has been unprecedentedly rapid. Never before has such a completely new technology been developed so quickly or so effectively, and so universally. Electronic techniques are now applied to all branches of science and engineering. A study of electronics is therefore central to any science or engineering course, and more and more people, in all walks of life, are going to be needing a basic knowledge of electronic technology.
It is true that electronics developed from the study of electricity. Early ideas about the way electric current could flow through conductors and through a vacuum led to the development of useful radio systems. It was possible to send messages around the world using what was, by today's standards, incredibly simple and crude equipment. The Second World War provided an urgent requirement for more sophisticated communication and other electronic systems. The invention of radar (radio direction finding and ranging) required a big step forward in theory and an even bigger step forward in engineering. The study of electronics gradually became an important subject in its own right, and the radio engineer became a specialized technician.
The development of television led to one of the most massive social changes that has taken place. Many households now possessed televisions, radios and record players. In some branches of industry, electronic systems became useful-but electronic devices not directly concerned with the wireless transmission of sound or pictures were still something of a curiosity.
Only in the early 1960s did electronics technology 'come of age' thanks to the work of three scientists, Bardeen, Brattain and Shockley, in the Bell laboratories in the USA. In 1957 they assembled the first working transistor.
1.1 THE MICROELECTRONIC REVOLUTION
In order to understand just how much impact the invention of the transistor was to have, it is necessary to realize that every electronic machine required the use of valves. Valves will be described in Section 5, but for the time being it is enough to know that valves are rather inconvenient devices for handling electrons. Valves are rather large, difficult to produce on a large scale, and extremely wasteful of power. The transistor, on the other hand, can be made quite small and uses relatively little power. It is much cheaper to make than a valve and lends itself to mass-production techniques. More importantly, the transistor can be made very small. There is a theoretical limit to the size of a transistor, but this limit is astonishingly tiny. Using transistor technology it became possible to make electronic circuits very complicated and very small. It is quite difficult to get an idea of the difference in scale between electronic devices using valves and electronic devices using microelectronic technology. It does not give a very valid comparison to look at a radio receiver of the 1930s and compare its size with a modern transistor radio. The size of the transistor radio is not limited by technology but rather by the size of the person who is expected to operate it. Transistor radios can be made extremely small, but the lower limit of smallness is reached when it becomes impossible to operate the controls! A more useful comparison can be made by looking at computers. One of the first working, large-scale computers was made in the late 1940s. It occupied an area about equal to that of an hotel suite, and used as much power as a medium-sized street of houses. It was vastly expensive, and vastly unreliable-on average a valve had to be changed once every ten minutes.
I am fortunate enough to own a computer of substantially more power than that of the giant of the 1940s. It cost me less than one week's pay, and fits neatly into my jacket pocket. It will operate for approximately 300 hours on two tiny batteries and I would be surprised if it ever went wrong.
All this gives an indication of the scale of change that has taken place as a result of the development of electronics, and of the 'microelectronic revolution' sparked off by the invention of the transistor.
1.2 ELECTRONICS TECHNOWGY TODAY
Most of the development in electronics has taken place since 1960. Inevitably there have been large changes in the way the subject is taught, and indeed in what is taught. Solid-state technology has even led to a change in the way we look at the physics of the atom. Models of the atom which work well for electronics based on the relatively crude 'valve' technology are often not sufficient for a useful description of modern microelectronic components.
This guide is divided into three parts. Part I is a revision of basic electricity. This part of the guide goes rather faster than the other two parts.
It will provide you with sufficient knowledge of electricity to enable you to understand the rest of the guide. It is not, however, a complete study of the subject but will be a useful memory-jogger for anyone who has studied electricity at school but who needs to be reminded of what was learnt there.
Part II deals with linear electronics. Broadly, this is a study of electronic components and systems that deal with continuously varying quantities and represent these quantities by means of an electrical analogue. Electronic systems that involve this technology include television and radio, audio and video reproduction equipment, and a number of electronic instruments.
Part III deals with digital electronics. In digital electronics, systems deal only with numbers, usually represented by the presence or absence of an electrical signal. Digital electronic systems include, of course, computers and calculators, and a number of electronic instruments. Digital electronics is probably the most rapidly developing branch of electronics technology.
Various functions previously carried out by linear systems are now being dealt with digitally--one major example is studio-quality audio recording and reproduction. A sound signal can now be represented as a stream of numbers, and can be recorded and replayed in this form to give a totally reproducible and high-fidelity audio signal. Most commercial sound recording studios now use digital techniques for recording.
1.3 ELECTRONIC SYSTEMS
It used to be necessary for students of electronics to understand at a basic physical level the way in which electronic systems worked. This is still true in so far as a student must have a thorough understanding of the physics of electronic devices. However; it is no longer necessary--or indeed possible-for students to understand the detailed workings of individual circuits. A microelectronic counter, for example, may be extremely complex in its actual operation. If a manufacturer has some novel circuit, he may be very reluctant to publish details of the way the device works. In the case of very complex microelectronic systems--such as microprocessors--it would be a major study to examine in detail the operation of just one such device. The technologist today is concerned with systems, and with the operating parameters of the individual circuit components.
An individual circuit component in this context may be a complete amplifier or counter. The manufacturer will provide very complete data, and provided the user is fully aware of the device's characteristics, it is no longer necessary to understand the precise details of a device's internal functioning. For reasons outlined above, such information may be rather difficult to obtain.