Electronics guide > Analogue integrated circuits
Analogue integrated circuitsWell, the last chapter was pretty well jam-packed with information about transistors.
If you remember, we saw that transistors are very important electronic components.
They may be used in one of only two ways: in digital circuits, or in analogue circuits
— although many, many types of digital and analogue circuits exist.
In terms of importance, transistors are the tops. They’re far more important
than, say, resistors or capacitors, although in most circuits they rely on the other
components to help them perform the desired functions. They’re the first electronic
components we’ve come across which are active: they actually control the flow of
electrons through themselves, to perform their function — resistors and capacitors
haven’t got this facility, they are passive and current merely flows or doesn’t
flow through them.
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.
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