1 00:00:01,710 --> 00:00:16,710 Well, in second official, we have already studied some important electronic components such as a light-dependent resistor, potentiometer, and so on. 2 00:00:16,710 --> 00:00:29,129 So, we will use these components in this year, but we will also study one very important 3 00:00:29,129 --> 00:00:33,590 component that is new for you, which is transistor. 4 00:00:33,590 --> 00:00:45,789 So in this lesson we are going to review semiconductors, the diodes and its way of work. 5 00:00:46,710 --> 00:00:56,630 sister which is new and that are basically the component more characteristic in 6 00:00:56,630 --> 00:01:09,060 analogical electronic. Firstly, well, we know that the materials can be 7 00:01:09,060 --> 00:01:18,060 divided into insulators and conductors but there are also some materials and 8 00:01:18,060 --> 00:01:23,299 also some components that sometimes can be conductors and sometimes can be 9 00:01:23,299 --> 00:01:34,840 insulators. It depends of the quantity of energy. One of these is silicon. Silicon 10 00:01:34,840 --> 00:01:51,000 as you can see in this slide, is solid at a temperature, at our temperature. So what 11 00:01:51,000 --> 00:02:03,540 happens if you, for example, give silicon sun energy such as light or heat, the links 12 00:02:03,540 --> 00:02:09,979 between two atoms of silicon in the net can be broken. 13 00:02:09,979 --> 00:02:17,300 So if one of these links is broken, what happens? 14 00:02:17,300 --> 00:02:25,340 Well you have an electron that can move in the net of silicon, so the silicon changes 15 00:02:25,340 --> 00:02:34,460 from insulator to conductor but you also have a hole in the net of silicon so a silicon can 16 00:02:35,419 --> 00:02:43,099 be a conductor because it has electron free electrons and also free holes electrons are 17 00:02:43,099 --> 00:02:52,789 negative charge, negative loads, and holes are positive loads. 18 00:02:52,789 --> 00:03:04,250 Can also improve if you change one atom of silicon, one atom of silicon in the net is 19 00:03:04,250 --> 00:03:15,210 changing to other kind of atoms, for example, if you change one silicon and 20 00:03:15,210 --> 00:03:25,969 exchange the silicon with a boron, we have one less electron, what you have is 21 00:03:25,969 --> 00:03:36,969 is a hole, so this is a conductor because it has positive chairs that can move on the net. 22 00:03:36,969 --> 00:03:44,969 If you have instead of silicon, phosphorous, phosphorous has an extra electron, 23 00:03:44,969 --> 00:03:56,969 So you have a semiconductor type negative because you have a free electron in the net of silicon. 24 00:03:56,969 --> 00:04:22,290 So, what happened? Well, usually we have one part of silicon with excess of holes or positive charge and another part with excess of electrons or negative charge. 25 00:04:22,290 --> 00:04:50,709 In this case what you have is a diode. So it's the first component with this solid. What happened? That obviously in the joint zone the electrons and holes tend to culminate so you have an electric current because of this. 26 00:04:50,709 --> 00:05:15,430 If you have electric current, you also have a voltage, so you can draw what happens, what is the relationship or the ratio between the voltage in the diode and the current in the diode, which is something intrinsic of the diode. 27 00:05:15,430 --> 00:05:27,750 it just only depends on the numbers of church holes and electrodes, so it just only depends on 28 00:05:29,670 --> 00:05:41,189 how the makers have made this diodes. It's not something extrinsic, it's something external 29 00:05:41,189 --> 00:05:46,930 of the diode is something that depends just only the material. 30 00:05:46,930 --> 00:05:51,370 So this is the characteristic of the diode. 31 00:05:51,370 --> 00:06:04,069 Other thing is when connect the diode to a power supply, for example battery. 32 00:06:04,069 --> 00:06:05,069 What happens? 33 00:06:05,069 --> 00:06:08,930 You can connect the diode in two ways. 34 00:06:08,930 --> 00:06:18,750 which is the way in the directed polarization in this case what you are doing with the external 35 00:06:18,750 --> 00:06:27,170 churches is push internal shakers but you can also connect the yodo against the internal 36 00:06:27,170 --> 00:06:39,350 current in this case is inverse polarization if you do pushing the 37 00:06:39,350 --> 00:06:45,170 internal current obviously you have this case is in this part of the 38 00:06:45,170 --> 00:06:54,050 characteristic cure but in the you do against what usually happen is that you 39 00:06:54,050 --> 00:07:07,269 need to overcome voltage and sometimes it can burn the diodes, just only thinner diodes 40 00:07:07,269 --> 00:07:12,209 can work in these conditions. 41 00:07:12,209 --> 00:07:24,649 So in this case, what you have is that, depending on the external parameters, the warp point 42 00:07:24,649 --> 00:07:26,449 is different. 43 00:07:26,449 --> 00:07:38,389 So you can have the characteristic of the diodes and also the warp line. 44 00:07:38,389 --> 00:07:47,050 And between two lines there is an international point, which is the warp point. 45 00:07:47,050 --> 00:07:52,069 And in this point there are the gases still constant that you do. 46 00:07:52,069 --> 00:08:02,209 Logically, you usually use a point which is also always in saturation. 47 00:08:02,209 --> 00:08:13,589 So although it is true that the work point in a diodo is not always the same, it does 48 00:08:13,589 --> 00:08:20,589 not always have the same voltage and the same current, we can consider that the voltage 49 00:08:20,589 --> 00:08:33,639 in a diodo is always 0.7 volts. 50 00:08:33,639 --> 00:08:46,059 And you can also have other solid components, in this case is transistor. 51 00:08:46,059 --> 00:08:58,580 Transistor can be bipolar or unipolar, it depends of how you make this transistor. 52 00:08:58,580 --> 00:09:09,899 Well in a bipolar transistor what you have, you have three parts, base, emitter and collector. 53 00:09:09,899 --> 00:09:15,399 The parts depending of the external dopage. 54 00:09:15,399 --> 00:09:25,299 So you can have a PNP transistor or NPN transistor. 55 00:09:25,299 --> 00:09:38,159 In any case, the current in emitter is the addition of the current of base and collector. 56 00:09:38,159 --> 00:09:43,100 But the sense of the current are different in any case. 57 00:09:43,100 --> 00:09:58,059 So the way you have to connect the transistor to the battery depends on the type of transistor. 58 00:09:58,059 --> 00:10:04,419 You must take into consideration the polarity. 59 00:10:04,419 --> 00:10:14,299 Well, as you have in the diodo, in this case you have a characteristic of transistor. 60 00:10:14,299 --> 00:10:20,139 A characteristic curve of transistor is in this slide in blue. 61 00:10:20,139 --> 00:10:26,179 So in this characteristic you can distinguish three zones. 62 00:10:26,179 --> 00:10:40,340 a zone in which you have the transistor cut, so it works as an open interrupter, 63 00:10:40,980 --> 00:10:48,500 there is another zone which is the saturation region in which the transistor 64 00:10:48,500 --> 00:11:02,539 always is like a closed interrupter and the voltage is 0.2 volts below and between these 65 00:11:02,539 --> 00:11:16,980 zones the voltage between collector and emitter and connector depends of the current that are 66 00:11:16,980 --> 00:11:28,129 through the base so is the active zone and as the same happened in the in the 67 00:11:28,129 --> 00:11:39,950 diodo in this case you can have difference a good point one point it 68 00:11:39,950 --> 00:11:48,029 depends the external a external condition it depends of the voltage of 69 00:11:48,029 --> 00:11:56,750 battery and the pencil the current that the battery makes that are in through the 70 00:11:57,549 --> 00:12:09,230 the the transistor we will do a problem in which you can understand all of this another important 71 00:12:09,230 --> 00:12:17,230 thing is the relationship between the current that you have through the base and the current 72 00:12:17,230 --> 00:12:32,769 that you have in the emitter. Transistor is a small amplification, so the relationship between 73 00:12:32,769 --> 00:12:42,990 the current in the collector and in the base is what usually called transistor gain. Well, 74 00:12:42,990 --> 00:12:58,379 very often is 100 more or less. Well in this case for example you have an example or in which you 75 00:12:58,379 --> 00:13:10,500 can calculate all the parameters we have in this case how you can calculate for example the current 76 00:13:10,500 --> 00:13:19,679 in the collector, the current in the base and so on. So the only thing that you have to do is 77 00:13:19,679 --> 00:13:30,120 have an application of Ohm's law. But we will do another example that can clarify you all of this. 78 00:13:30,120 --> 00:13:45,279 Apart from the transistor, you can also have, for example, other types of transistors, which 79 00:13:45,279 --> 00:13:54,179 are usually called unipolar, but what happens nowadays is that, for example, in transistor, 80 00:13:54,179 --> 00:14:07,019 we come to states current cutoff and saturation. So you can associate this state with O and 1. 81 00:14:07,019 --> 00:14:16,919 So you can transform analogic electronic into digital. And nowadays we usually do, 82 00:14:16,919 --> 00:14:33,000 because digital electronic is very easy and it's very useful and it's what we are doing nowadays.