Microprocessors are built from silicon-based transistors that function as electronic switches, controlling the flow of electricity to produce binary outputs of one or zero. Understanding how silicon's semiconductor properties enable this switching behavior is foundational to understanding how modern computing hardware works.
Microprocessors & Transistors
We've talked quite a bit now about transistors and microprocessors and integrated circuits, and how these microprocessors and integrated circuits use a lot of these transistors within them. Now let's take that to another degree and look at how these microprocessors work, why they're so important, and why we consider them switches.
Our story begins with an element called silicon. Silicon is a basic element that's found on the periodic table. In fact, you might have heard of Silicon Valley — that's just because it's a big tech hub here in the United States. Silicon is an element that we build these transistors out of. It's a very common element, and you can find silicon even in sand.
But there's something really special about silicon, something that it doesn't really share with many other elements on the periodic table. Most stuff that you find on the periodic table is either conductive, meaning electricity can flow through it, like copper, or not conductive, like glass, and those are called an insulator. Silicon is unique in many ways, because we can add a couple of substances to it to make it a semiconductor — that is, sometimes it will conduct electricity and sometimes it won't conduct electricity.
This is what a transistor looks like, and several of the components in here are actually made of silicon. What we'll do is put power on one side, so we've got power coming in on one side, and then we've got it grounded out the other side. Or maybe it's powering something — maybe it's a light bulb, there's something on the other side.
Now, electricity is not going to flow through here until we apply power right here. We'll put a plus right there, as we're applying power. Actually, because who knows if this is 5 volts, maybe it's 10 volts, maybe it's 12 volts, maybe it's 120 volts — who knows what this is — instead of putting power, we're going to say one there. If we have a one representing this power element here, then we'll have electricity flow through that silicon to the other side, and we'll get a one as an output over here. However, if we don't have any electricity applied here, what's going to happen is it's going to change the makeup of this area right here, electricity won't flow through, and we're going to get a zero on the other side.
I'm going to change the way this looks and make it look like a button instead, like a switch, because that's essentially what it is. We press a one right here, so we're pressing down on the button — that would be equivalent to one, that means we're sending voltage to it — then power is going to flow through here, because it's going to make a contact there. However, if we don't press this button, or a zero, that means electricity can't flow through this conductor right here.
That's why, if you can see it, there are actually three different prongs to this. We have a power that we apply to it, and then we have the output of it of one or a zero, and then we have the input to this of a one or zero. If we put a one as an input into it, then power flows from the positive to the output, and if we put a zero into this, then the power can't flow from the positive to the output.
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