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Although we have already studied some electronic devices and some electronic elements, there are the inputs, such as, for example, potentiometer and so on.

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We just only have two outputs which are diode and servo motor. The diode is like a bulb, it emits light, but just only when you connect correctly.

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Otherwise, it doesn't work.

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So, we are going to study the diode.

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Firstly, we are going to study the semiconductor materials and in my explanation you can understand

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what is a extrinsic semiconductor, what is a diode, its characteristics and its work point.

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We are going to talk about some types of diodes and the application of the others.

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Well, what is an intrinsic semiconductor?

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Semiconductors are material or substance that they are in the nature and they can be conductor

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insulators depending on the circumstances. One example of this kind of

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substances could be silicon. Silicon has four electrons in the atom

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constitution. So to link with other silicon atoms it usually share one

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electron with each silicon neighbor as you can see in this picture. So if you

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heat or if there is a very energetic life or other kind of energy, it is possible that

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one of these links can be broken by energy.

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So some electrons are free now and they can move the same way as electrons move in metals.

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So it's a conductor substance.

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Apart from this, the positive charges is created by holes in the net of silicon.

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So not also the electrons can move, but holes can move also.

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So there are two types of conduction in this material now.

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One by negative churches, electrons, and another one by holes or positive churches.

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This can be also explained using the band theory.

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In the band theory, the semiconductors are systems with a gap between the conductor band

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and the, between balance bands and conduction bands, there is a very small gap.

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So it's very easy that the electrons can jump from the balance band to conduction band.

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then the material is a conductor material and as as the way as the same way is conductor because

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there are holes there are positive churches and there are also negative churches both of them can

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move in the in the silicon net but we can we can do this by by replacing a

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atom of silicon in the net of silicon by replacing this atom for example if you

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replace an silicon atom with a boron atom, boron has one electron less, so it

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creates, each boron atom can create a hole in the silicon net and this

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substance is a conductor system because the holes can move in the

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in the net. On the other hand if you put an atom which has more electrons than

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for example an antimonium-1, electrons can move in the net and this is a

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semi extrinsic semiconductor type N. Here could be what happens if I have one

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part with a p semiconductor and another one with n semiconductors obviously they

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tend to return to a combine and eliminate the holes and electrical extra

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So there is a current, there is an intrinsic current in this type of device, which is usually called diode. This is a diode loop.

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And if you put an external current, obviously, if you connect in the same way, this current can be strengthened.

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On the other hand, if you want a current in opposite direction, that only can be possible

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if you are if your current is bigger than the intrinsical current and this effect can be drawn

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and it's the what's usually called characteristic of a diode the shape of the characteristic is

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well it's the same for all of the diodes but the values of this depends on the

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type of of the diode depends how many holes and how many electrons it has so

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it's a difference however there's always a more or less a saturated zone which is

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more or less 0.3 to germanium or 0.37 to silicon which is the

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the maximum volta, the saturator of volta. I built a circuit in which there is a diode,

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as you can see in this slide. Firstly, you need, obviously, resistance and using the Ohm's law,

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So it's very easy to know or to have a relationship between the voltage in the diode and its current.

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So you can draw this relationship in the characteristic cube and there is a point which is a junction between two mathematical functions.

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This point is usually called working point and it shows the best conditions in which this diode can work. It's current and it's voltage.

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and is a characteristic and it's very important to design a circuit with diodes.

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There are various types of diodes, obviously, but this is the symbol of a normal diode

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and you should connect the positive with the positive and the negative with the negative.

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But we can also have lead, which emits light, which is bright. And another which is important also is zener, which you can use connecting with inverse polarity.

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The normal diode is usually used in electronics to do rectificators, for example, or it is

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also used to show if it has a current, or nowadays it is also used to give light because

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is very very cheap and is very environmental friendly uh and so on to do a circuit using a

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diode LED you should use 220 ohms resistance and it's really easy to do

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that and obviously you you should do in a protoboard we will use diode with the

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Arduino board so we will study better

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this kind of circuits. It is all for today