The intensive effort of electronics to increase the reliability and performance of its products while reducing their size and cost has led to the results that hardly anyone would have dared to predict.
The evolution of electronic technology is sometimes called a revolution. What we have seen has been a steady quantitative evolution: smaller and smaller electronic components performing increasingly complex electronic functions at ever higher speeds. And yet there has been a true revolution: a quantitative change in technology has given rise to qualitative change in human capabilities.
It all began with the development of the transistor.
Prior to the invention of the transistor in 1947 its function in an electronic circuit could be performed only by a vacuum tube. Tubes came in so many shapes and sizes and performed so many functions that in 1947 it seemed audacious to think that the transistor would be able to compete except in limited applications.
The first transistors
had no striking advantage in size over the smaller tubes and they were more costly. The one great advantage the transistor had over the best vacuum tubes was exceedingly low power consumption. Besides they promised greater reliability and longer life. However, it took years to demonstrate other transistor advantages.
With the invention of the transistor all essential circuit functions could be carried out inside solid bodies. The goal of creating electronic circuits with entirely solid-state components had finally been realized.
Early transistors, which were often described as being a size if a pea, were actually enormous on the scale at which electronic events take place, and therefore they were very slow. They could respond at a rate of a few million times a second; this was fast enough to serve in radio and hearing-aid circuits but far below the speed needed for high-speed computers or for microwave communication systems.
It was, in fact, the effort to reduce the size of transistors so that they could operate at higher speed that gave rise to the whole technology of microelectronics.
A microelectronics technology has shrunk transistors and other circuit elements to dimensions almost invisible to unaided eye.
The point of this extraordinary miniaturization is not so much to make circuits small per se as to make circuits that are rugged, long-lasting, low in cost and capable of performing electronic functions at extremely high speeds. It is known that the speed of response depends primarily on the size of transistor: the smaller the transistor, the faster it is.
The second performance benefit resulting from microelectronics stems directly from the reduction of distances between circuit components. If a circuit is to operate a few billion times a second the conductors that tie the circuit together must be measured in fractions of an inch. The microelectronics technology makes close coupling attainable.
It may be helpful if we say a few words about four of the principal devices found in electronic circuits: resistor, capacitors, diodes and transistor. Each device has a particular role in controlling the flow of the electrons so that the completed circuit performs some desired function.
During the past decade the performance of electronic systems increased manifold by the use of ever larger numbers of components and they continue to evolve. Modern scientific and business computers, for example, contain 109 elements; electronic switching systems contain more than a million components.