on video How MOSFET Transistor Works | What It Can do

 How MOSFET Transistor Works | What It Can do

I show how MOSFETs work in real life, and explain where they can be used and how to check them. With this simple circuit the transistor works as a switch.

In the video I use IRF540N MOSFET with N-channel, it has three terminals: Gate, Drain, and Source. MOSFET transistor requires very little current to turn on while it can deliver a much higher current to a load, so it works as an amplifier.

MOSFET transistors are used to amplify and switch electronic signals.

(First of all, I made some edits to the HTML code for this I'ble, which is optimized for the desktop site, so it may not be ideally viewed on a mobile device.)

Transistors are arguably the most important electronic component in use today. They are nearly everywhere, in nearly every electronic device we use. Radios, phones, computers, game consoles, TVs, cars, toys... the list goes on. Without them, life would be radically different.

The idea of the transistor was first developed and patented in 1925 by Julius Edgar Lilienfeld, but manufacturing techniques for the required materials were not good enough to produce a high enough quality crystal and so development and testing came much later. William Shockley, John Bardeen and Walter Brattain of Bell Labs spent many years and LOTS of money researching and developing what became the point-contact transistor, which was a PNP type transistor and was successfully demonstrated as a voice amplifier on December 23, 1947. It It wasn't until 1950 that Shockley developed the bi-polar transistor (BJTs) that became so ubiquitous, and still is today. For some practical applications of BJTs, see my BJT Instructable.

Julius Lilienfeld had actually described what we know now as the field effect transistor, or FET (more specifically he predicted the JFET), in his patent of 1925, and it was the FET that the guys at Bell Labs were trying to produce when they developed the point-contact transistor. It wasn't until 1960 that the first MOSFET was introduced by Dawon Kahng and Martin Atalla.

MOSFETs differ from BJTs in that BJTs require that a current be applied to the base pin in order for current to flow between the collector and emitter pins. On the other hand, MOSFETs only require a voltage at the gate pin to allow current flow between the drain and source pins. MOSFETs actually have a very high gate impedance by design, which makes them very good at reducing the amount of wattage a circuit requires to run. One of the first transistor based computers required 150 watts, but it used point-contact transistors. That doesn't seem like much compared to now, but it only had 200 transistors and 1300 diodes. My dad's Casio watch from 1990 had more computing power and didn't require nearly that much power. (Thank goodness. Can you imagine the burn marks?) Thankfully computers now use MOSFETs almost exclusively in their designs, so they don't require as much power. As indicated by the title, I will be going over some uses for MOSFETs in this Instructable. This is not intended to be an exhaustive resource, simply a "get started" point so you can get on building.

  Parts and Some Theory

There are lots of different types of MOSFETs out there, so picking a specific one to use can be a little bit overwhelming. For the projects here I will be using ZVP2110A (datasheet) and ZVN2110A (datasheet) for pretty much everything. They are a bit outdated, but more than adequate for our purposes here. The ZVP is P-channel, meaning that it requires a relatively negative signal at the gate pin to function. The ZVN is N-channel, requiring a relatively positive signal to function. I know it seems backwards, but if you think of negative as "holes" and positive as "plugs", you can't make "holes" and "holes" work, you need "holes" and "plugs" to have a smooth "surface" over which the electrons can flow. P-channel and N-channel MOSFETs - I happen to have the ZVP and ZVN MOSFETs laying around, so I used those. The package type for these is known as E-type (image below), and is very similar to the TO-92 package but the rounded side is flatter. More often than not you will find MOSFETs in the TO-220 package or similar (image below). MOSFETs in the TO-220 package are usually power MOSFETs and are designed to handle higher current loads. Either package will work for the following examples. I also found a 2N7000 in my parts bin, which has a TO-92 package, so they come in all shapes and sizes. Note - there is no set standard for pin assignments between package types! Always double check your datasheets to make sure you know which pin is which.various resistors - nominal values from 100Ω - 100kΩ will be fine. Exact values will be given as needed.

various electronic bits - motors, LEDs, switches, etc. Stuff that can be switched on or amplified.

breadboard, jumper wires, 9V battery & battery clip.

Logic ICs. These are totally optional, but MOSFETs find their best application in logic circuits. Specific ICs will be listed as needed.

The image below shows the two types of schematics symbols associated with MOSFETs. (It should be noted here that the schematics shown are only for enhancement type MOSFETs. There are also depletion type, and the difference is that enhancement “turn on” when voltage is applied, whereas the depletion type “turn off”. We will deal Only with enhancement types here.) The three pins are labeled Gate, Drain, and Source. (FYI - for BJTs, these are labeled Base, Collector, and Emitter and serve the same basic functions). Carefully note the orientation of the three pins. It's very easy to switch the MOSFET around backward, so always double check your datasheets for the MOSFET you are using to ensure the correct pin orientation. The ZVNs and ZVPs that I'm using have a different pin orientation than most MOSFETs that use the TO-220 package.

Take a look at the datasheet again for the ZVN2110A. As always there is a lot of information on the datasheet. Pay close attention to maximum ratings. Always give yourself some room between operating and max values and stay well away from max values. When you operate near max values, you generate more heat than is needed, and you will lose performance as well as shorten the life of the transistor. Get a transistor with a higher rating if needed.

In order for N-channel MOSFETs to work, the gate voltage (VG) must be more positive than the source voltage (VS). This is often noted as VGS and a frequent minimum value for VGS is 0.6-1.0V. Note that according to the datasheet, the ZVN can handle a VGS of +/-20V, but it only takes between 0.8V (min) and 2.4V (max) to open the gate. This means that you can apply the same supply voltage to the gate as well as the drain of your MOSFET without worrying about performance issues. That will make more sense later on.

Another factor to keep in mind is the drain-source voltage (VDS). VDS cannot be less than VGS or the MOSFET simply won't work.

For P-channel MOSFETs, we need to invert all of the above. VDS should be the most negative value, VS should be the most positive value, and VGS should be less than VS but higher than or equal to VDS.

  A Simple Switch

MOSFETs are really easy to "saturate", which just means that they are fully open, and they are dead reliable for very fast switching between their saturation and cut-off regions (fully on and fully off regions). This makes them wonderful switches, especially for high power applications like motors, lamps, etc. In most cases, you can use the same power supply that you are using for your high power device to operate the MOSFET as well, using a mechanical switch to apply the gate voltage. The image below shows exactly that type of application. (Alternatively, you can also use an electronic signal, like from a microcontroller, to activate the MOSFET. This is extremely common, and useful, since the output pins on microcontrollers are not designed for high power applications. Also, be sure to check the gate threshold voltage for the MOSFET and compare it to the microcontroller output pin voltage. Some MOSFETs require more voltage than some microcontrollers can output.)

 How MOSFET Transistor Works | What It Can do

I show how MOSFETs work in real life, and explain where they can be used and how to check them. With this simple circuit the transistor works as a switch.

In the video I use IRF540N MOSFET with N-channel, it has three terminals: Gate, Drain, and Source. MOSFET transistor requires very little current to turn on while it can deliver a much higher current to a load, so it works as an amplifier.

MOSFET transistors are used to amplify and switch electronic signals.

(First of all, I made some edits to the HTML code for this I'ble, which is optimized for the desktop site, so it may not be ideally viewed on a mobile device.)

Transistors are arguably the most important electronic component in use today. They are nearly everywhere, in nearly every electronic device we use. Radios, phones, computers, game consoles, TVs, cars, toys... the list goes on. Without them, life would be radically different.

The idea of the transistor was first developed and patented in 1925 by Julius Edgar Lilienfeld, but manufacturing techniques for the required materials were not good enough to produce a high enough quality crystal and so development and testing came much later. William Shockley, John Bardeen and Walter Brattain of Bell Labs spent many years and LOTS of money researching and developing what became the point-contact transistor, which was a PNP type transistor and was successfully demonstrated as a voice amplifier on December 23, 1947. It It wasn't until 1950 that Shockley developed the bi-polar transistor (BJTs) that became so ubiquitous, and still is today. For some practical applications of BJTs, see my BJT Instructable.

Julius Lilienfeld had actually described what we know now as the field effect transistor, or FET (more specifically he predicted the JFET), in his patent of 1925, and it was the FET that the guys at Bell Labs were trying to produce when they developed the point-contact transistor. It wasn't until 1960 that the first MOSFET was introduced by Dawon Kahng and Martin Atalla.

MOSFETs differ from BJTs in that BJTs require that a current be applied to the base pin in order for current to flow between the collector and emitter pins. On the other hand, MOSFETs only require a voltage at the gate pin to allow current flow between the drain and source pins. MOSFETs actually have a very high gate impedance by design, which makes them very good at reducing the amount of wattage a circuit requires to run. One of the first transistor based computers required 150 watts, but it used point-contact transistors. That doesn't seem like much compared to now, but it only had 200 transistors and 1300 diodes. My dad's Casio watch from 1990 had more computing power and didn't require nearly that much power. (Thank goodness. Can you imagine the burn marks?) Thankfully computers now use MOSFETs almost exclusively in their designs, so they don't require as much power. As indicated by the title, I will be going over some uses for MOSFETs in this Instructable. This is not intended to be an exhaustive resource, simply a "get started" point so you can get on building.

  Parts and Some Theory

There are lots of different types of MOSFETs out there, so picking a specific one to use can be a little bit overwhelming. For the projects here I will be using ZVP2110A (datasheet) and ZVN2110A (datasheet) for pretty much everything. They are a bit outdated, but more than adequate for our purposes here. The ZVP is P-channel, meaning that it requires a relatively negative signal at the gate pin to function. The ZVN is N-channel, requiring a relatively positive signal to function. I know it seems backwards, but if you think of negative as "holes" and positive as "plugs", you can't make "holes" and "holes" work, you need "holes" and "plugs" to have a smooth "surface" over which the electrons can flow. P-channel and N-channel MOSFETs - I happen to have the ZVP and ZVN MOSFETs laying around, so I used those. The package type for these is known as E-type (image below), and is very similar to the TO-92 package but the rounded side is flatter. More often than not you will find MOSFETs in the TO-220 package or similar (image below). MOSFETs in the TO-220 package are usually power MOSFETs and are designed to handle higher current loads. Either package will work for the following examples. I also found a 2N7000 in my parts bin, which has a TO-92 package, so they come in all shapes and sizes. Note - there is no set standard for pin assignments between package types! Always double check your datasheets to make sure you know which pin is which.various resistors - nominal values from 100Ω - 100kΩ will be fine. Exact values will be given as needed.

various electronic bits - motors, LEDs, switches, etc. Stuff that can be switched on or amplified.

breadboard, jumper wires, 9V battery & battery clip.

Logic ICs. These are totally optional, but MOSFETs find their best application in logic circuits. Specific ICs will be listed as needed.

The image below shows the two types of schematics symbols associated with MOSFETs. (It should be noted here that the schematics shown are only for enhancement type MOSFETs. There are also depletion type, and the difference is that enhancement “turn on” when voltage is applied, whereas the depletion type “turn off”. We will deal Only with enhancement types here.) The three pins are labeled Gate, Drain, and Source. (FYI - for BJTs, these are labeled Base, Collector, and Emitter and serve the same basic functions). Carefully note the orientation of the three pins. It's very easy to switch the MOSFET around backward, so always double check your datasheets for the MOSFET you are using to ensure the correct pin orientation. The ZVNs and ZVPs that I'm using have a different pin orientation than most MOSFETs that use the TO-220 package.

Take a look at the datasheet again for the ZVN2110A. As always there is a lot of information on the datasheet. Pay close attention to maximum ratings. Always give yourself some room between operating and max values and stay well away from max values. When you operate near max values, you generate more heat than is needed, and you will lose performance as well as shorten the life of the transistor. Get a transistor with a higher rating if needed.

In order for N-channel MOSFETs to work, the gate voltage (VG) must be more positive than the source voltage (VS). This is often noted as VGS and a frequent minimum value for VGS is 0.6-1.0V. Note that according to the datasheet, the ZVN can handle a VGS of +/-20V, but it only takes between 0.8V (min) and 2.4V (max) to open the gate. This means that you can apply the same supply voltage to the gate as well as the drain of your MOSFET without worrying about performance issues. That will make more sense later on.

Another factor to keep in mind is the drain-source voltage (VDS). VDS cannot be less than VGS or the MOSFET simply won't work.

For P-channel MOSFETs, we need to invert all of the above. VDS should be the most negative value, VS should be the most positive value, and VGS should be less than VS but higher than or equal to VDS.

  A Simple Switch

MOSFETs are really easy to "saturate", which just means that they are fully open, and they are dead reliable for very fast switching between their saturation and cut-off regions (fully on and fully off regions). This makes them wonderful switches, especially for high power applications like motors, lamps, etc. In most cases, you can use the same power supply that you are using for your high power device to operate the MOSFET as well, using a mechanical switch to apply the gate voltage. The image below shows exactly that type of application. (Alternatively, you can also use an electronic signal, like from a microcontroller, to activate the MOSFET. This is extremely common, and useful, since the output pins on microcontrollers are not designed for high power applications. Also, be sure to check the gate threshold voltage for the MOSFET and compare it to the microcontroller output pin voltage. Some MOSFETs require more voltage than some microcontrollers can output.)