In this video tutorial I am going to explain to you how the MOSFET transistor works and how you should use it. Do not miss it. My name is Aurelio Cadenas and without further ado, this begins, we can classify the field effect transistors that we have already seen . is the junction transistor (junction field transistors) which can be n-channel or p-channel and the one we are going to see now is the mosfet transistor also called IGFET (insulated gate field effect transistor) or field effect transistor metal oxide semiconductor (MOSFET) there are two types enrichment and impoverishment which is used more than enrichment okay and we have both n-channel and p-channel in this video tutorial I will explain the n-channel enrichment and you will see how easy it is to understand too the p-channel one, the internal structure, knowing it will allow you to understand how the mosfet transistor works, as you already know, what all transistors want to achieve is regulate a current that we are going to circulate in this case from drain to source and to control that current you already know that the field effect transistors use a voltage the JFETs used the voltage between gate and source here we are going to use this voltage between the gate and the source but if you realize we have four terminals if you look at its internal structure we have four terminals what happens is that this terminal which is called the substrate is always internal or most of the time you will find it attached to the source terminal that internally therefore what you are going to see is a transistor with three terminals okay Drain gate and source well as you can see we have a substrate that is a p-type semiconductor and two zones of n-type semiconductor here what there are are many electrons there are free ones willing to conduct and many selections many electrons contribute many free electrons there are to conduct the current we have that in tend it as electrons that I can represent with balls like billiard balls okay and when a force is applied to a ball this ball collides with the first one and here it is immediately ejected so that we could consider that the current is based on collisions Assuming that the ones we have there that represent the electrons are billiard balls because understanding how the physics of transistors works is a bit complex, okay then we always make a good simile because in this case with balls and push one and this one from here would come out in movement is okay if we chain them together because we would have a current then here what it is about is that if I place a resistor and a battery here and I want a current to circulate here this resistor at hand becomes rd and this voltage vdd we are going to erase here what is going to happen that this current is not going to exist because if you realize trainer and source here I do not have electrons so that they can push each other and circulate the current ok so I have to get the electrons that I have here because I also have holes I also have holes here but the electrons that I have here in this p-type material I have to manage to accumulate the accumulate the here accumulate them here to form an electron channel here ok how do I do that very simple if I apply here a positive terminal and here a negative terminal that is to say a voltage was applied to the gate more positive than the substrate or what is the same a voltage between gate and it was like this with this polarity as here I have a positive potential the electrons automatically go like crazy towards this area the higher this voltage the more electro point and then what the manufacturer tells me gives me a graph and tells me that until apply here a voltage usu gs greater than a certain value that the manufacturer calls it urges that threshold 3 young liz th and that this manufacturer voltage does not define it as a fixed value but as a value between a value of 2 and 3 a value of 2 and 4 for example depends on the transistor logically and at the minimum value and a maximum value or a typical value and then from this voltage because before a current will not begin to circulate so the manufacturer gives me a burga such that lectern where we represent the current and sude depending on the voltage gs the higher this voltage is than that we are getting more electrons here or more acts of this channel then more easily more It will be easy for the current to circulate here, okay, when the current circulates here, yes, look at the following on the door, I have a metal, okay, that is, this is a metal , this here, striped in blue, is an oxide, which is an insulator, it is an insulator, okay and this area here is a semiconductor it's worth a semiconductor this right here that's why these are called mos transistors metal they give semiconductor oxide but if you realize that's a capacity metal is a conductor the semiconductor tor we can also consider it as a conductor or semiconductor and in the middle what I have is an insulator and in the middle what I have is an insulator that is between the gate and the source or between the gate rather and we have a capacity that what does it mean that if here I applied a variable positive voltage if this voltage is lower imagine the threshold voltage is two I bought some moss transistor and I have to check the threshold voltage I am going to increase this voltage from zero and when I reach 2 automatically they would be here with an ammeter living a current ok so now what I want to complete is the following: current flows from the substrate and source gate, that is, current will flow through here current flows through here the answer would be yes until this very small capacity is charged if I applied a voltage here continuous this this capacitor this capacitance as soon as it dries no current flows through the gate that time is very short because the capacitance e s very small and the time constant the product of r by c is very small therefore we say that through the gate there will be no current there will be no current as long as we have a continuous voltage if what we have is a continuous signal but button and always positive values we have a continuous signal pulse theory if there is current consumption by the gate in voltage changes in voltage changes because the capacitor is charged it is discharged to that charge it discharges it charges it discharges and while it is charging it discharges if current flows, the higher the frequency of the voltage that I apply to the gate, the more consumption there will be of current, it is okay if what I am adapting is a constant voltage, there is no consumption, nothing more than at the beginning it is okay and well, when the source ends then these transistors do not have this advantage and disadvantages that if they work if they work in commutation well they have a small consumption a small consumption through the gate well it is small Specially , we must bear in mind that these transistors are very sensitive because they are controlled by voltage , so if I leave it like this, I leave it like that and touch here with my hand with my finger there automatically that transistor can start conducting because because our body has static electricity, especially when we are rubbing, okay, we have static electricity and that static electricity is enough because it is a voltage, it is enough to excite the transistor so that this does not happen, what we do is place a resistance to ground here For example, 10 houses is fine and it is the transistor, even if we touch here there will be no triggering of it, so you will always see a circuit such that it is logically good, we put a high value so that the current consumption there is small, fine well then we are going to put here a variable battery and we will also start a battery vary the power supply that we can vary and that we can vary we will see r how this transistor behaves for this we are going to make it an interesting graph that the manufacturers provide me with this graph the parts the manufacturers provide me with it ok let's admit that the threshold voltage is 2 volts ok then for a voltage gs for a voltage gs here For a voltage vg of 2 volts, it is clear that the transistor does not conduct, that is, even if I increase this voltage and the voltage between the computer and the source increases, the current that the transistor allows to pass is zero, that is, the transistor will be cut off . it would be the graph constructed for a voltage gs for example of 2 volts 2 volts or less well what happens if I increase this voltage and I get a voltage vgs of 25 volts what is going to happen well what is going to happen is that as we increase this battery the current is going to increase until it reaches a value in which it no longer increases, the evil no longer increases, that is, there will be a linear zone that as e the voltage increased the current also increases it is a resisted behavior as it happened in the transistor j feet what current do we have here well for this voltage vgs of 2.5 volts it depends on the transistor okay we are going to take a transistor because it works very well with ttl logic which is and rl 530 okay this is going very well to work either an arduino or with raspberry well if we go to the datasheet to the datasheet this value would be 05 amps okay this would be in amps fine and this value from which the transistor begins to saturate How will you obtain it? Well, very simply, you will obtain it by making the voltage gs that we are applying minus the voltage, one arm is valid in this case, since we are applying 2.5 volts and the threshold voltage we have said that it is two volts, volts, because that value will be 05 volts, this value will be 05 volts we're going to increase this a little bit more we're going to increase this to 3 volts gs 3 volts and we'll see the same as the current as I increase from zero this pa pa pa pa pa it increases, increases, increases, increases until it reaches a value from which the current no longer increases and its what values this is, how easy it is 3 in this case minus 2 that is to say this will be a volt ok what current we have here the current that we would see in the data if we look at the data yes and we have 5.5 amps is the current that we would have out there well more voltage gs more voltage hey let's go for example to a voltage gs of 5 volts that we build for nothing we increase we increase here the voltage increases the current increases the voltage un su ds great great great until there comes a time when it is already saturated it does not increase anymore it does not increase anymore how much would that current be worth is 30 amps at 30 amps how much is this value this value this value it would be 5 minus 2, this value would be 3 volts, that is, it will resist in the zone or , as it happened with the jota fed transistor, it must be fulfilled that if we have here a gs voltage of 5 volts, the voltage of that the voltage between source and source has to be less than 3 volts okay because if it is greater than 3 volts if it is more than 3 volts the transistor is saturated the transistor is saturated okay it behaves like a current source that is to say the equivalent circuit of the moss transistor is the same as that of the getafe in the resistive zone we will have a resistance between the computer and the source we will always put the gate in isolation we connect the resistance from rd and this would be the valid circuit for the voltage or less that arises that minus raises its t is valid otherwise we would have a current source that simple these are the equivalent electrical circuit of the transistor we have this would be an n-channel transistor and for a voltage use of that higher dv surge - v subte ht that simple and that simple we would work if the gs is 5 volts here we would always have to have less than 3 volts if we have more than 3 volts it is that we are with this circuit and this source would be from a 30 amps is worth 30 but it's around here well look at a very important detail for a gs voltage of 5 volts for a gs voltage of 5 volts if we are working in this zone the resistive zone, that is, in this zone the transistor behaves more or less like a resistance like a resistance what value will that resistance have well that resistance rd that will be the increase in voltage use of that is to say this variation in voltage which is three volts 3 volts / of the variation in current which is 30 which are the variation in current that is 30 amps that is 0.1 or mines is worth 0.1 or mines and of this resistance if we make the transistor work at some point on this line we have a resistance of 0.1 mines it is worth if we look at the datasheet the datasheet this is given to me by the manufacturer and it tells me that the rds even when the transistor is active when the path is there in the resistive line zone for a gs voltage of 5 volts the manufacturer tells me and a current here and a current 9 amps here the rds resistance is 0 16 shoulders this is given to me by the manufacturer so note that the advantage of these transistors is that they can conduct a lot of current and dissipate very little power but well when the transistor is already in switching we go from cut to the resistive zone and in this reactive zone is when the transistor has less voltage at its ends and the current that we wanted circulates, for example if 9 amps circulate the network resistance m says the manufacturer that it is 0.16 is worth Well, new periods squared by 0.16, that would be the power consumed by the transistor when it is there conducting, it is valid when the cutoff is present, because the current is very, very, very , very small and practically in power it is 0, it is negligible, however, bipolar transistors are valid. the power they consume is higher than the mosfet transistors, therefore the morphe transistors are used a lot in power, it is worth this characteristic that they have well finally a clarification how to differentiate an enrichment and impoverishment mosfet transistor the impoverishment one is used less it would represent itself ok that is to say this line is continuous ok then this is the impoverishment transistor and this is the transistor enrichment modes well the channel n and p channel very easy look this is the channel that is not formed that is why it goes to dashed lines here the channel is formed continuous line this arrow represents that of a diode it represents that of a pn diode therefore in this it would be a channel in this one that would be a p-channel look at the diode there this would be p and this would be in the p-channel how to work with transistors we see this would be a transistor we see while this would be an in we have this is exactly the same the channel the channel is p so so we have to attract holes to the gate that means that this terminal has to be negative with respect to that here what we would do what we did was form a electron channel and therefore the gate would have to be positive to attract the electrons to the gate so here we work with voltages that is always greater than zero and here we work with negative gs voltages that are negative everything else is the same what we regulate is the current from drain to source the current and its d is all the same in the next video you will see how to place a mosfet transistor in computing how to calculate the resistance to place it in switching cutoff and saturation for example when we are going to connect it to a digital output of a microcontroller such as a wine or a raspberry of a mini computer such as a raspberry or vigon bond or any other ok don't miss it it will be very interesting and if you liked the video please give it a thumbs up I like thumbs up and if you want to be informed you just have to subscribe to my channel activate the bell so that youtube notifies you every time I upload a video thanks and see you to the next class well thanks for your attention until the end of the video you can ask me any questions or comments about it if you don't want to miss any of my classes subscribe to my channel to chains and don't forget to activate the bell so youtube will notify you every time I upload a video thanks and until the next class see you later
