Page 36 - Curriculum Visions Dynamic Book

Silicon and integrated circuits
Silicon has always been an important element in our lives through the silicates that surround us.
But through the development of transistors and integrated circuits, this element has, in recent years, helped to transform the ways we do things, perhaps more than any other element on Earth. Here are some of the components that have made this revolution possible.
Transistors
The transistor lies at the heart of the electronics revolution.
It is the fundamental building block of all computers and
other solid-state circuits. Its invention in 1948 allowed large, cumbersome, unreliable and energy-consuming valves (vacuum tubes) to be replaced with small, robust, reliable devices that used very little energy.
Transistors, developed from junction diodes, have two junctions, which can be arranged to give two quite different effects. In one type the junctions are arranged back to back. This type has a single chip of silicon doped with one metal in the middle and a different metal at both ends. The central region
of the transistor is called the base and it controls the flow of current through the chip from one end (called the emitter) to the other end (called the collector).
This kind of transistor is often used as an amplifier. A tiny current generated by, say, a voice from a microphone, arrives
at the base of the transistor. A much larger current is flowing through from the emitter to the collector. The small base current interferes with this flow, making changes in the large current that mirror the changes in the small current. If this larger current is fed into a loudspeaker, an amplified sound is heard.
Alternatively, the same transistor can also be made to act as a very fast switch. This is how it is used in computers.
Since the first transistors were developed there have been many advances in how they are made. In particular, special types of transistor (known as MOSFETS or metal oxide semiconductor field effect transistors,) are simpler and need fewer components to complete their circuits. These are used as the main elements in microprocessors, where they are grouped by their thousands to make an integrated circuit or IC, commonly known as a “chip”.
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