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Starting electronics
Transistors, being active, can control current so that they
can be turned into amplifiers or switches depending on the
circuit. There’s nothing magical about this, mind you, we’re
not gaining something for nothing! In order that, say, a transistor
can amplify a small signal into a large one, energy has
to be added in the form of electricity from a power supply.
The transistor merely controls the energy available from this
power supply, creating the amplification effect.
They’re important for another reason, however. They are
small! They can be made by mass-production techniques,
almost as small as you can imagine, and certainly many times
smaller than you could see with your bare eyes. This in itself
is no big deal — imagine trying to solder a transistor into a
circuit which was so small you couldn’t even see it! Transistors
of the types we’ve seen so far are purposefully made as
large as they are, just so we can handle them.
Integrated circuits
But the big advantage of transistors, especially tiny transistors,
is that many of them may be integrated into a single circuit,
which is itself still very small. To give you an idea of what we’re
talking about, modern integrated circuits (well, what else
would you call them?) have been made with over a quarter of
a million transistors, all fitting onto one small silicon chip only
about forty square millimetres or so! Now this sort of integration
represents the ultimate in human achievement, remember, but
processes are being improved every year and integrated
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