WEBVTT - TechStuff Tidbits: What is a diode?

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<v Speaker 1>Welcome to tech Stuff, a production from I Heart Radio.

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<v Speaker 1>Hey there, and welcome to tech Stuff. I'm your host

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<v Speaker 1>Jonathan Strickland, Diamond executive producer with I Heart Radio, and

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<v Speaker 1>how the tech are you well today? For a tech

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<v Speaker 1>Stuff Tidbits episode, I thought I would talk about what

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<v Speaker 1>diodes are and what they do. So they are one

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<v Speaker 1>of the basic components of modern electronics. So what the

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<v Speaker 1>heck are they? I'm sure you've heard of them, even

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<v Speaker 1>if you're not familiar with electronics, you've heard the term diodes. Heck,

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<v Speaker 1>l e ED. That's a light emitting diode. You have

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<v Speaker 1>lots of stuff all around you that has diodes in it.

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<v Speaker 1>So it's easiest to explain diodes by starting with the

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<v Speaker 1>kind of of function they fill within electronics. So a

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<v Speaker 1>die ode is sort of like a check valve in

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<v Speaker 1>a plumbing system. So a check valve in a in

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<v Speaker 1>a pipe, for example, will open when water flows in

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<v Speaker 1>one direction. The water will push against the valve and

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<v Speaker 1>the valve will lift up and water can flow through.

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<v Speaker 1>But if the water starts to come back in the

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<v Speaker 1>opposite direction, then the water is going to push the

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<v Speaker 1>valve cap back down and the valve will close and

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<v Speaker 1>the water can't keep going. So this way you can

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<v Speaker 1>allow water to flow one way through the pipe, but

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<v Speaker 1>it can't come back, which is important in some types

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<v Speaker 1>of you know, hydraulic systems, that sort of stuff. So

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<v Speaker 1>diodes do something similar. They allow electricity to flow in

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<v Speaker 1>one direction in a circuit, but they prevent it from

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<v Speaker 1>going the opposite way. Now, a quick word on that.

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<v Speaker 1>When we talk about current and flow, things get a

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<v Speaker 1>little confused due to the fact that electrical engineers described

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<v Speaker 1>current as moving from positive to negative. But if we

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<v Speaker 1>look at the at current as the flow of electrons,

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<v Speaker 1>we know that this is the opposite of what actually happens.

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<v Speaker 1>It doesn't go positive to negative. Electrons move from negative

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<v Speaker 1>to positive. This is because electrons themselves have a negative charge,

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<v Speaker 1>which means they're repelled by other negative charges, right like

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<v Speaker 1>repels like, and opposites attract, So electrons are attracted to

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<v Speaker 1>positive charges. So if you've got a big old bunch

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<v Speaker 1>of electrons crammed in together somewhere, they're all desperately trying

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<v Speaker 1>to get away from each other. But if you then

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<v Speaker 1>create a pathway where electrons can travel to a place

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<v Speaker 1>where there's a positive vibe. They're gonna rush through that

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<v Speaker 1>pathway to get to the positive place because no one

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<v Speaker 1>wants to hang out at a party where everyone as

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<v Speaker 1>negative all the time, So they're so eager to get

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<v Speaker 1>over to the positive place. You could even make them

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<v Speaker 1>do work along the way. This is the basis of electronics.

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<v Speaker 1>That electrons move from negative to positive, and along the

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<v Speaker 1>way you can make them do work because they just

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<v Speaker 1>want to get to that positive place. Man, they will

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<v Speaker 1>do whatever it is they need doing, assuming they've got

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<v Speaker 1>enough behind them to get the job done. Now that's

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<v Speaker 1>a pretty clumsy analogy, but it does fit anyway. There

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<v Speaker 1>are a lot of electrical engineering textbooks that talk about

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<v Speaker 1>what we would call conventional current. Conventional current is the

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<v Speaker 1>positive to negative flow. This is how Ben Franklin would

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<v Speaker 1>have talked about it. Uh And unfortunately that's just not

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<v Speaker 1>what's happening on a on an actual physics level, but

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<v Speaker 1>on an electrical engineering level. You can often see diagrams

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<v Speaker 1>that will depict current as flowing positive to negative. So

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<v Speaker 1>if you ever come across descriptions that talk about current

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<v Speaker 1>this way, it's from an electrical engineering perspective. And by

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<v Speaker 1>the way, this does have its uses. It's not that

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<v Speaker 1>this is this is to a point where it's going

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<v Speaker 1>to mess you up unless you're looking at a diagram

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<v Speaker 1>and you're making, uh, the opposite assumption based on the diagram. Instead,

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<v Speaker 1>it's useful for talking about specific systems. So I don't

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<v Speaker 1>mean to completely dismiss it, but it is kind of

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<v Speaker 1>funny to me. But I am going to talk more

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<v Speaker 1>about the electron flow description of current, So that means

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<v Speaker 1>going negative to positive, because that's what's actually happening. If

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<v Speaker 1>you were able to somehow visualize the electrons as they

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<v Speaker 1>move through the system, that's how it would go. All right,

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<v Speaker 1>let's get back to diodes. So let's say you're putting

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<v Speaker 1>together a simple circuit with a diode and you've got

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<v Speaker 1>a light bulb connected, and then you're going to connect

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<v Speaker 1>a power source of battery. Now, because diodes only allow

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<v Speaker 1>current to flow in one direction, if you've installed the

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<v Speaker 1>diode the wrong way around, it will actually prevent electricity

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<v Speaker 1>from moving through the circuit and the bulb won't light up.

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<v Speaker 1>If you flip the diode around, then it allows the

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<v Speaker 1>electricity to flow through the circuit and the light bulb

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<v Speaker 1>comes on. So when the diode faces one way, it's

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<v Speaker 1>behaving like an insulator. It's it's preventing the flow of electrons.

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<v Speaker 1>If you flip it around, it acts like a conductor.

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<v Speaker 1>It conducts the flow of electrons um And it turns

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<v Speaker 1>out the yeah, diode is a semiconductor component. It can

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<v Speaker 1>act as both a conductor or an insulator depending upon

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<v Speaker 1>the situation. A diode positioned to allow current to flow

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<v Speaker 1>is what we call in the forward bias. Forward means

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<v Speaker 1>that electricity can flow through the diode. If it is

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<v Speaker 1>positioned to act as an insulator, it is in the

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<v Speaker 1>reverse bias. It will prevent electricity from flowing in that direction.

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<v Speaker 1>But how like, what is it about a diode that

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<v Speaker 1>allows this to happen. Well, that requires a bit of physics, alright.

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<v Speaker 1>So a conductive material has a lot of what we

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<v Speaker 1>would call free electrons, meaning these are electrons that are

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<v Speaker 1>not in fully packed electron shells. They can be boosted

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<v Speaker 1>out with just a little bit of energy and then

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<v Speaker 1>be free roaming electrons. But uh that so you just

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<v Speaker 1>have to add some energy, right and then once you do,

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<v Speaker 1>then the electrons will start to move through the material

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<v Speaker 1>and they will be moving towards the most positive area

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<v Speaker 1>connected to this material. And then if you have an insulator,

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<v Speaker 1>while you've got electrons that are very tightly packed, right,

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<v Speaker 1>there's no movement available, like there's no room in the end,

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<v Speaker 1>so there's no place for an incoming electron to go,

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<v Speaker 1>and it kind of just bounces off and you know,

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<v Speaker 1>it acts almost like a force field. Now, to make

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<v Speaker 1>a semiconductor really useful, we actually have to dope it

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<v Speaker 1>because semiconductive material has fairly tightly packed UH atoms and

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<v Speaker 1>fairly tightly packed electrons. So without doping it, without introducing impurities,

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<v Speaker 1>then you're not gonna be able to easily make it

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<v Speaker 1>conduct It will act as more of an insulator than

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<v Speaker 1>a conductor. So we're just introducing something else in there

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<v Speaker 1>to change up the structure really and you can actually

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<v Speaker 1>dope semiconductor material in one of two ways. You can

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<v Speaker 1>dope it with atoms that actually have extra electrons in

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<v Speaker 1>their outermost shell, which creates an in type semiconductor or

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<v Speaker 1>negative side. Or you could pack in atoms of stuff

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<v Speaker 1>that have fewer electrons in their outer shell, which means

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<v Speaker 1>we they have holes, they have places where electrons could occupy.

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<v Speaker 1>This is p type semiconductor material. Now, let's talk about

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<v Speaker 1>silicon to give an example. So a silicon atom has

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<v Speaker 1>four electrons in its outermost electron shell, but it's an

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<v Speaker 1>electron shell that can accommodate up to eight electrons. It's

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<v Speaker 1>just that silicon doesn't have eight and its outermost as four.

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<v Speaker 1>But if you get a lot of silicon atoms together

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<v Speaker 1>and they form covalent bonds with one another, then each

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<v Speaker 1>silicon atom is going to bond with four other silicon

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<v Speaker 1>atoms and they're gonna share outer most electrons, so that

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<v Speaker 1>each atom, if you were to look at it and

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<v Speaker 1>just kind of ignore the fact that there are atoms

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<v Speaker 1>around it, it it would appear that there are eight electrons

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<v Speaker 1>and net outer most shell and then would be all

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<v Speaker 1>full up. So, in other words, when silicons all together

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<v Speaker 1>as a as a material, as opposed to a single atom,

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<v Speaker 1>then it's acting like it's got full electron shells and

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<v Speaker 1>its outermost shell. So what you want to do is

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<v Speaker 1>introduced something else, like phosphorus, which has five electrons in

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<v Speaker 1>its outermost shell. So silicon has four, phosphorus has five.

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<v Speaker 1>If you start putting phosphorus, if you dope phosphorus into silicon.

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<v Speaker 1>Then these silicon atoms, some of them are bonding with phosphorus.

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<v Speaker 1>But that means there's this extra electron that has nowhere

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<v Speaker 1>to go, right, because you only have enough room for

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<v Speaker 1>four of those electrons in that oldermost shell to bond

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<v Speaker 1>with other atoms. The fifth one is kind of loose

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<v Speaker 1>on its own. So now you have electrons that could

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<v Speaker 1>easily freely move through this material. Then, if you want

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<v Speaker 1>to make a P type semiconductor, you dope silicon with

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<v Speaker 1>atoms that have fewer than four electrons in their outermost shells.

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<v Speaker 1>For example, aluminum as three. So aluminum bonding with silicon

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<v Speaker 1>means there's gonna be an extra space for an electron.

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<v Speaker 1>You get a hole there. Uh, And so you have

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<v Speaker 1>this N type or negative semiconductor material that has an

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<v Speaker 1>excess of electrons and thus has a negative charge. And

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<v Speaker 1>then you have a P type semiconductor material that has

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<v Speaker 1>an excess of electron holes, and we describe this as

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<v Speaker 1>having a positive charge. So if we put IN type

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<v Speaker 1>against P type, we create a diode. So you have

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<v Speaker 1>N type semiconductor material on one side and P type

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<v Speaker 1>semiconductor material on the other side, and where the two

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<v Speaker 1>meet is called the P n junction. We'll describe its

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<v Speaker 1>function after this quick break. Okay, so we have the

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<v Speaker 1>P n junction where the P type semiconductor material comes

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<v Speaker 1>into contact with the N type of semiconductor material. What

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<v Speaker 1>happens then, Well, if you remember, the N type semiconductor

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<v Speaker 1>or the N type side of the diode has an

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<v Speaker 1>excess of electrons, the P type has an excess of

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<v Speaker 1>electron holes. So you would think, oh, well, then all

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<v Speaker 1>the electrons are just gonna move, all the free electrons anyway,

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<v Speaker 1>the excess ones are going to move from the N

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<v Speaker 1>type side to the P type side, and it'll just

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<v Speaker 1>equalize out. That's not exactly what happens. What does happen

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<v Speaker 1>is some of the electrons do move over from N

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<v Speaker 1>type to P type, some of the holes move from

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<v Speaker 1>P type to N type, and it creates what is

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<v Speaker 1>called a depletion zone at the P N junction. It

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<v Speaker 1>creates this electric field, and that electric field has a

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<v Speaker 1>charge there that prevents more electrons from N type to

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<v Speaker 1>move over to the P type side. So it's like

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<v Speaker 1>there's this this force field. It's a weak force field,

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<v Speaker 1>but it exists, and in order to get through it,

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<v Speaker 1>you have to add more energy to the system. But

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<v Speaker 1>without that added energy, the electrons just can't make the jump.

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<v Speaker 1>If you think about it, it's kind of like let's

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<v Speaker 1>say you're well, you're a kid, and you're running around

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<v Speaker 1>in the woods and you come up on an old

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<v Speaker 1>like little dry creek bed that's created a ditch, and

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<v Speaker 1>the ditch is not wide, but it's not super wide.

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<v Speaker 1>If you get a running start, you can jump over

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<v Speaker 1>that ditch. But if you were to try and jump

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<v Speaker 1>just from a standstill, you never make it right. You'd

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<v Speaker 1>fall into the ditch. You have to have enough energy

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<v Speaker 1>to make it all the way across. That's the same

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<v Speaker 1>way with these diodes. Without that energy, the electrons aren't

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<v Speaker 1>going anywhere. They are essentially blocked by the depletion zone

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<v Speaker 1>and the electric field that it creates. All right, So

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<v Speaker 1>then if we then attach the P type side of

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<v Speaker 1>the diode, the annode side, to the paw stive end

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<v Speaker 1>of the battery, and then we take the cathode side

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<v Speaker 1>of the diode on the N type and we attach

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<v Speaker 1>that to the negative side of the battery. Well, now

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<v Speaker 1>the battery is providing enough voltage, enough pressure, enough energy

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<v Speaker 1>to push those electrons from the inside over to the

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<v Speaker 1>PA side, and then they continue they're attracted to the

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<v Speaker 1>anode because the anode is positively charged. Now that it's

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<v Speaker 1>connected to the positive terminal of a battery, and you

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<v Speaker 1>get the flow of electricity, And as long as the

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<v Speaker 1>battery is still attached, it's going to continue to provide

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<v Speaker 1>that voltage that will allow the current to continue to flow.

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<v Speaker 1>So electric electrons will continue to go into the N

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<v Speaker 1>type side and push over to the P type side

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<v Speaker 1>and then continue their journey over to the positive terminal

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<v Speaker 1>of the battery. And it'll do this till the battery

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<v Speaker 1>runs out of a charge or essentially doesn't have enough

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<v Speaker 1>voltage enough energy to push those electrons over the depletion zone.

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<v Speaker 1>But then what happens if you turn the battery around, right?

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<v Speaker 1>What if you what if you put the battery in backward, Well,

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<v Speaker 1>now you're gonna have these opposite charges. You're gonna have

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<v Speaker 1>a positive charge over at the cathode side, over at

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<v Speaker 1>IN type side of the diode. You're gonna have a

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<v Speaker 1>negative charge over at the anode side, over the P

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<v Speaker 1>type side of the diode. And that negative charge on

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<v Speaker 1>the anode is going to attract all the holes over

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<v Speaker 1>to that side. The positive side over at the cathode

0:14:36.160 --> 0:14:38.280
<v Speaker 1>is going to attract all the electrons to that side.

0:14:38.560 --> 0:14:41.040
<v Speaker 1>The middle of your diode is going to become a

0:14:41.120 --> 0:14:46.040
<v Speaker 1>much larger depletion zone. So in other words, there is

0:14:46.120 --> 0:14:50.000
<v Speaker 1>now a much larger barrier that you have to jump.

0:14:50.040 --> 0:14:52.120
<v Speaker 1>It's like that ditch that you came across in the

0:14:52.120 --> 0:14:54.720
<v Speaker 1>woods has turned into the Grand Canyon. You are just

0:14:54.920 --> 0:14:57.400
<v Speaker 1>not gonna make it across that ditch no matter how

0:14:57.440 --> 0:15:04.800
<v Speaker 1>fast you run, except with diodes it's not quite the same.

0:15:05.600 --> 0:15:11.480
<v Speaker 1>So with diodes, you can create enough voltage to jump

0:15:11.600 --> 0:15:16.720
<v Speaker 1>that barrier. The problem is when you do this, then

0:15:17.160 --> 0:15:20.840
<v Speaker 1>you kill the diode and potentially you fry whatever circuit

0:15:21.080 --> 0:15:25.520
<v Speaker 1>it was connected to because you've you've added enough voltage

0:15:25.520 --> 0:15:31.080
<v Speaker 1>to overcome this depletion zone. But for normal operation, that

0:15:31.200 --> 0:15:33.840
<v Speaker 1>depletion zone is enough to prevent current from flowing. So

0:15:33.880 --> 0:15:36.040
<v Speaker 1>that's why we say diodes are kind of like a

0:15:36.160 --> 0:15:38.880
<v Speaker 1>check valve. I guess in a way, you can think

0:15:38.920 --> 0:15:40.880
<v Speaker 1>of it as a check valve in a pipe where

0:15:40.960 --> 0:15:43.600
<v Speaker 1>you have just put so much water pressure that it

0:15:43.680 --> 0:15:47.480
<v Speaker 1>breaks the check valve inside the pipe at the pipe itself,

0:15:47.880 --> 0:15:51.080
<v Speaker 1>possibly might break two and that would be very similar

0:15:51.120 --> 0:15:54.560
<v Speaker 1>to what we're talking about in circuitry, where a diode

0:15:54.560 --> 0:15:57.400
<v Speaker 1>has had enough Essentially negative voltage is what it comes

0:15:57.440 --> 0:15:59.920
<v Speaker 1>down to, because you're you're talking about a reverse bias

0:16:00.000 --> 0:16:05.720
<v Speaker 1>in this point up to break through that depletion zone. Okay,

0:16:05.960 --> 0:16:10.240
<v Speaker 1>that's generally what how diodes work, right that they are

0:16:10.640 --> 0:16:14.440
<v Speaker 1>kind of a one way lane for electricity. But what

0:16:14.520 --> 0:16:18.320
<v Speaker 1>do we actually use them for. So in some ways

0:16:18.360 --> 0:16:20.800
<v Speaker 1>we use it exactly as I mentioned, like a way

0:16:20.840 --> 0:16:24.760
<v Speaker 1>to control the way electricity can flow, but we also

0:16:24.840 --> 0:16:27.440
<v Speaker 1>use them for other stuff like light emitting diodes. Obviously

0:16:27.480 --> 0:16:30.640
<v Speaker 1>emit light, they are l e ed s. We use

0:16:30.720 --> 0:16:35.480
<v Speaker 1>these in everything from light strips to ultra high definition televisions,

0:16:36.120 --> 0:16:39.760
<v Speaker 1>but we also use diodes to do other things. So

0:16:40.080 --> 0:16:43.440
<v Speaker 1>one examples, you can use it as a rectifier. So

0:16:43.920 --> 0:16:46.880
<v Speaker 1>a rectifier is something that allows you to convert alternating

0:16:46.920 --> 0:16:51.120
<v Speaker 1>current into direct current. So direct current is easy, right,

0:16:51.160 --> 0:16:53.160
<v Speaker 1>you have current that flows in one direction. This is

0:16:53.200 --> 0:16:56.800
<v Speaker 1>what batteries do. It goes from the negative terminal into

0:16:56.840 --> 0:17:00.160
<v Speaker 1>the positive terminal. That's it. It cannot go the other way.

0:17:00.360 --> 0:17:02.040
<v Speaker 1>It's not going to go from the positive terminal to

0:17:02.080 --> 0:17:04.600
<v Speaker 1>the negative terminal unless we're talking about conventional current, which

0:17:04.600 --> 0:17:09.480
<v Speaker 1>we're not. So so it's that's direct current. It's always

0:17:09.520 --> 0:17:11.359
<v Speaker 1>going to go in that direction, and most of our

0:17:11.400 --> 0:17:17.000
<v Speaker 1>electronics run on direct current. Alternating current reverses the current

0:17:17.119 --> 0:17:20.280
<v Speaker 1>direction many times a second. We describe them and hurts.

0:17:20.320 --> 0:17:22.679
<v Speaker 1>So if it's like a hundred and twenty hurts current,

0:17:23.040 --> 0:17:26.200
<v Speaker 1>that means a hundred twenty times a second the direction

0:17:26.240 --> 0:17:29.359
<v Speaker 1>of current is switching, going one way and then the

0:17:29.400 --> 0:17:32.720
<v Speaker 1>other way. It does this add twenty times a second. Now,

0:17:32.720 --> 0:17:35.880
<v Speaker 1>getting into why it does this would get into more

0:17:36.200 --> 0:17:39.000
<v Speaker 1>than what the scope of this episode is about. But

0:17:39.119 --> 0:17:42.119
<v Speaker 1>this is what we use in order to transmit electricity

0:17:42.160 --> 0:17:46.439
<v Speaker 1>great distances because alternating current can make use of something

0:17:46.480 --> 0:17:49.399
<v Speaker 1>called transformers, which are more than meets the eye, but

0:17:49.440 --> 0:17:54.639
<v Speaker 1>they're not robots in disguise. No transformers are used to

0:17:54.840 --> 0:17:58.520
<v Speaker 1>change the voltage of alternating current, and stepping up the

0:17:58.600 --> 0:18:02.359
<v Speaker 1>voltage or increasing the pressure if you will, means you

0:18:02.359 --> 0:18:07.000
<v Speaker 1>can push the electricity further down power lines and then

0:18:07.000 --> 0:18:09.639
<v Speaker 1>you would step down the voltage. You would decrease the

0:18:09.720 --> 0:18:13.080
<v Speaker 1>voltage when you were ready to transmit electricity from the

0:18:13.080 --> 0:18:16.600
<v Speaker 1>power lines. To say a home or a business. But

0:18:16.720 --> 0:18:19.000
<v Speaker 1>we still have to be able to change the alternating

0:18:19.040 --> 0:18:22.960
<v Speaker 1>current into direct current so that our actual electronics can

0:18:23.000 --> 0:18:24.960
<v Speaker 1>make use of it, and a diode can do that

0:18:25.000 --> 0:18:28.080
<v Speaker 1>because a diode will only allow current to flow in

0:18:28.080 --> 0:18:31.639
<v Speaker 1>one direction, So essentially it would only allow a C

0:18:31.880 --> 0:18:35.080
<v Speaker 1>current to flow through half the time when the direction

0:18:35.119 --> 0:18:38.240
<v Speaker 1>of the A C current matches the direction the forward

0:18:38.280 --> 0:18:40.800
<v Speaker 1>direction of the diode. The other half of the time,

0:18:40.800 --> 0:18:44.480
<v Speaker 1>it would block electricity from from flowing because it's against

0:18:44.480 --> 0:18:47.760
<v Speaker 1>the diode. Now, this would mean that you would have

0:18:47.760 --> 0:18:52.240
<v Speaker 1>a pulsing direct current. So you could actually use collections

0:18:52.240 --> 0:18:54.639
<v Speaker 1>of diodes and some other components to make this a

0:18:54.680 --> 0:19:00.520
<v Speaker 1>more smooth operation, including enough diode so that whether the

0:19:00.560 --> 0:19:03.879
<v Speaker 1>electricity is traveling in one direction or the other, the

0:19:04.040 --> 0:19:07.240
<v Speaker 1>diodes create a pathway that allow the electronics to make

0:19:07.359 --> 0:19:10.720
<v Speaker 1>use of direct current. It's pretty cool. It's very difficult

0:19:10.760 --> 0:19:14.680
<v Speaker 1>to describe without the use of visual aids, but yeah,

0:19:14.720 --> 0:19:17.119
<v Speaker 1>diodes are incredibly important for that. We can also use

0:19:17.200 --> 0:19:20.680
<v Speaker 1>diodes with radio waves. Again, a deep discussion of radio

0:19:20.680 --> 0:19:23.600
<v Speaker 1>waves is beyond this, but you know you can encode

0:19:23.640 --> 0:19:26.399
<v Speaker 1>audio onto radio waves. That's how radios work. If you

0:19:26.440 --> 0:19:29.440
<v Speaker 1>tune into a radio station, you know the sound has

0:19:29.480 --> 0:19:33.800
<v Speaker 1>been encoded onto radio waves. We use diodes to extract

0:19:33.920 --> 0:19:37.960
<v Speaker 1>the audio from the carrier signal of the radio wave.

0:19:38.359 --> 0:19:41.399
<v Speaker 1>So yeah, they're really important components and I hope you

0:19:41.440 --> 0:19:44.600
<v Speaker 1>have a greater appreciation of them. And uh yeah, that

0:19:44.640 --> 0:19:47.399
<v Speaker 1>wraps up this tech stuff tidbits. I'll talk to you

0:19:47.440 --> 0:19:56.960
<v Speaker 1>again really soon. Y tech stuff is an I Heart

0:19:57.040 --> 0:20:00.119
<v Speaker 1>Radio production. For more podcasts from my heart ray you

0:20:00.560 --> 0:20:03.720
<v Speaker 1>visit the I Heart Radio app, Apple Podcasts, or wherever

0:20:03.800 --> 0:20:09.840
<v Speaker 1>you listen to your favorite shows. H