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Transistors
Hint:
Yes, that’s right, only two basic uses of a transistor exist, and every
transistorised circuit, every piece of electronic equipment, every
television, every radio, every computer, every digital watch and so
on, contains transistors in one form or another which do only one
of two things.
We’ve already seen the first of these two uses — an electronic
switch, where a tiny base current turns on a comparatively
large collector current. This may appear insignificant in itself,
but if you consider that the collector current of one transistor
may be used as the base current of a following transistor or
transistors, then you should be able to imagine an enormous
number of transistors inside one appliance, all switching and
hence controlling the appliance’s operation.
Incredible? Science Fiction? Well, let me tell you that the
appliance described here in extremely simple terms already
exists, in millions. We call the appliance a computer. And
every computer contains thousands if not millions of transistor
electronic switches.
We can see the second use of a transistor in the circuit of
Figure 8.12. From this you should be able to see that we’re
going to use a variable resistor to provide a variable base
current for the transistor in the circuit. The breadboard
layout of the circuit is in Figure 8.13. Before you connect the
battery, make sure the preset variable resistor is turned fully
anticlockwise.
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