Arduino pins can directly turn ON very low power components like small LEDs. MOSFETs are great if you need to switch ON and OFF more powerful devices that also may use higher input voltage than Arduino's 5V.
So, which type of MOSFET should you use? If you need to turn ON a device that consumes more power than an Arduino pin can provide, then you should use a Logic Level Enhancement-Type N-Channel MOSFET. It's easy to wire it up to be OFF by default and switched ON when Arduino pin goes HIGH. I have used 30N06L MOSFET to switch ON 12V motors and lamps.
Type MOSFET ID VGS p-channel enhancement type MOSFET (a) (b) Fig 6.1: Different types of power MOSFET. (a) Circuit symbols and transfer characteristics (b) Photograph of n-channel enhancement type MOSFET. From Fig 6.1 (a) it can be concluded that depletion type MOSFETs are normally ON type.
- A MOSFET transistor is the most commonly used type of field-effect transistor. MOSFET operation is achieved in two modes, based upon which MOSFET transistors are classified. MOSFET operation in enhancement mode consists of a gradual formation of a channel whereas, in depletion mode MOSFET, it consists of an already diffused channel.
- Power MOSFTs are used in many power supply and general power applications, especially as switches. Variant s include planar MOSFETs, VMOS, UMOS TrenchMOS, HEXFETs and other different brand names. FET, Field Effect Transistor, Tutorial Includes.
In this article, I will talk about different types of MOSFETs, and give the reasons why I think you most likely want to use an N-Channel MOSFET:
Logic leve N-Channel and P-Channel MOSFETs
Disclosure: Bear in mind that some of the links in this post are affiliate links and if you go through them to make a purchase I will earn a commission. Keep in mind that I link these companies and their products because of their quality and not because of the commission I receive from your purchases. The decision is yours, and whether or not you decide to buy something is completely up to you.
What Kinds of MOSFETs There Are?
MOSFET can be either Enhancement-Type or Depletion-Type and N-Channel or P-Channel. Roughly speaking, we have four different kinds:
- Enhancement-Type N-Channel
- Enhancement-Type P-Channel
- Depletion-Type N-Channel
- Depletion-Type P-Channel
All MOSFETs have Gate (G), Source (S), and Drain (D) pins. The voltage between Gate and Source (Vgs) determines if the current is flowing through Source and Drain or not. Each kind has its own logic of when the MOSFET is turned ON or OFF. I will explain it in detail in the next two chapters.
Symbols for MOSFETs:
A MOSFET is classified as Logic Level MOSFET if it gets fully turned on with Vgs in the range of 3 to 5 volts. If you use a 5V Arduino board, then all Logic Level MOSFETs should be OK. If you are using a 3.3V board, then you have to check that the MOSFET you are using is compatible with 3.3V switching.
Best Mosfets
Normal MOSFETs typically need Vgs to be 10V or more to be fully ON.
Enhancement-Type MOSFET vs Depletion-Type MOSFET?
Every MOSFET is either Enhancement-Type or Depletion-Type.
Of the two types, the more common Enhancement-Type is not conducting electricity, when Vgs (voltage between Gate and Source) is zero - 'Normally OFF.' Depletion-Type is logical inversions of that, and is conducting when Vgs is zero - 'Normally ON.'
For example, an Enhancement-Type N-Channel MOSFET with a pull-down resistor will be OFF while your Arduino pin is not initialized as output (the first few seconds on startup). But a Depletion-Type will be ON in the same conditions.
When deciding between those two types, you have to think of what do you want to happen while your controller board is not actively driving the MOSFET Gate. If you don't know, then pick the Enhancement-Type. It's easy to put a 10k resistor between the Gate and the Source, which makes it OFF by default.
In the rest of the article, all the examples are about Enhancement-Type MOSFETs. Everything also applies to the Depletion-Type, just the ON/OFF status would be inverted.
N-Channel MOSFET vs P-Channel MOSFET
The main difference between an N-Channel and a P-Channel MOSFET is that N-Channel usually goes to the Ground (-) side of the load (the device you are powering), and P-Channel to the VCC (+) side.
But why do you have to connect one to the negative and the other to the positive side?
Enhancement-Type ('Normally OFF') N-Channel MOSFET starts to conduct if Gate value is sufficiently higher than Source. For Logic Level MOSFETs, it's typically 3 to 5 volts. If you connect the Source to the Ground, then you can use a voltage between Ground (-) and VCC (+) to activate it.
If you decided to connect it to the VCC side of the load, then the value of the Source would also be very close to VCC. It means that you need to apply a higher voltage than VCC to the Gate to active the MOSFET. Typically you don't have this higher voltage readily available, and it makes more sense to connect the Source of an N-Channel MOSFET to Ground.
Enhancement-Type ('Normally OFF') P-Channel MOSFET is like an upside-down N-Channel MOSFET. It starts to conduct if Gate value is sufficiently lower than Source. If you connect the Source of a P-Channel MOSFET to VCC, then you can use a voltage between VCC (+) and Ground (-) to turn it ON and OFF.
Connecting it to the negative side of the load has a similar problem that the N-Channel MOSFET had. Only this time, Source would be too close to Ground. You would need to apply a negative voltage (compared to Ground) to the Gate to activate it.
It is easy to remember: you should connect the Source pin of an N-Channel MOSFET to the negative output of your power supply, and the Source pin of a P-Channel MOSFET to the positive output of your power supply.
The same rules apply to Depletion-Type N-Channel and P-Channel MOSFETs. Only ON and OFF state is inverted.
Why Prefer an N-Channel MOSFET to a P-Channel MOSFET?
Functionally you could design your circuit in a way that you could use either of them. If you have an Arduino that runs on 5V and the device you are turning ON also runs on 5V, then it doesn't even matter. You could use an N-Channel or P-Channel MOSFET as long as you wire it accordingly.
Then why prefer N-Channel over P-Channel?
- You can have a Common Ground between the 12V power source and your Arduino.
With a P-Channel MOSFET, you have to create a Common VCC instead of a Common Ground. But it's standard practice to have a Common Ground between connected devices and modules. You can easily have that with an N-Channel MOSFET.
- You can power your Arduino from the same 12V power source by connecting the Arduino's barrel jack or the Vin pin to the power supply.
The negative input of the barrel connector leads directly to Arduino Ground. When you are using an N-Channel MOSFET as a power switch, then that is not a problem. The Grounds are connected anyways. With a P-Channel MOSFET, we can't connect the negative output of the power supply to the Arduino Ground since the 5V pin has to be pulled up to the positive output of the power supply. By also connecting the Grounds, you will send 12 volts through the Arduino.
- N-Channel MOSFETs are more efficient than P-Channel MOSFETs.
It comes down to physics. N-Channel MOSFETs use electron flow as the charge carrier. P-Channel MOSFETs use hole flow as the charge carrier, which has less mobility than electron flow. And therefore, they have higher resistance and are less efficient. In other words, a P-Channel MOSFET will get hotter than an N-Channel MOSFET with higher loads.
There are use-cases where P-Channel MOSFET is preferred or even required. For example the Arduino self-power-off circuit needs both: https://circuitjournal.com/arduino-auto-power-off
We've posted several articles that discuss what determines a 'good motherboard for gaming,' but until today, haven't had the chance to properly define what some of the more important board components do. Oscillating clock crystals, MOSFETs, chokes, the VRM, and other low-level motherboard components are defined in this post.
Judging from our forums, motherboards are one of the more nebulous components for hardware -- they all feel similar to each other, and from a specs sheet, it looks like there's not much separating one board from another. Part of this is because Intel and AMD have moved several controllers to the CPU, part is because the deeper differentiators between quality are often not listed on a product spec sheet.
After numerous questions from a large reddit thread, we've decided to start a new video/article series exploring the components on the components -- or what comprises each individual piece of hardware. Starting with the motherboard made sense.
In this article and video, we'll explore how a VRM works, what a chipset does, and PCI-e functionality; part of this discussion answers the 'what is a MOSFET?' question, including further information on chokes, capacitors, and the composition of a voltage regulator module.
Let's start with our video, which addresses all of these topics in a more rapid form by proxy of an MSI Z87-G45 board; AMD boards use the same underlying architecture, so the information is relevant regardless of processor.
Motherboard Components: Defining a 'Good' Motherboard for Overclocking & Gaming
Motherboard Diagram - The Anatomy of a Motherboard
This diagram requires JavaScript enabled to work properly. Hover over the dots on the board to read about the components. If, for whatever reason, this diagram doesn't work on your browser or phone, you can refer to our JPG version.
Complementary Metal–Oxide Semiconductor: Responsible for retaining low-level settings; can be removed to reset BIOS and OC/RAID settings (or for troubleshooting). Must be replaced once depleted.
'>Misc. Chips & ICsA - The Networking chip, or NIC. This is what processes your network I/O (often handles ethernet communications and processing).
B - Audio Chipset, often RealTek or an aftermarket option. Processes and cleans audio signals for sound comms.
C - Oscillating Clock Crystals, found throughout the motherboard. These aid in accurate frequency multiplying ('multipliers') and in timings / time keeping.
'>PCI Express InterfaceA - PCI-e x1 is often used for video capture cards, audio cards, and other low-bitrate expansion devices.
B - PCI-e x16/x8 slots are used for high-bitrate video devices. An x16 slot has 2x the visible pins of an x8 slot. PCI-e 3.0 x16 bandwith is 16GB/s; x8 is 8GB/s. PCI-e 2.x x16 bandwidth is 8GB/s; x8 is 4GB/s, etc.C - PLX/PEX Chips can multiplex PCI-e lanes by processing them multiple times, effectively creating an artificially-bolstered amount of lanes for video devices. Necessary for triple/quad-GPU arrays.
'>Front I/O HeadersA - USB2.0 headers connect front panel USB2 to the board.
B - 1394 Firewire headers connect Firewire to the board.
C - Front Panel Switches connect the buttons and LEDs to your board. Check the manual for correct mounting locations.
D - TPM Header, or Trusted Platform Module, integrates advanced security functions (biometric print storage, for instance) to protect the machine.
E - HD Audio headers connect your FP audio to the board.
'>BIOS & Error CheckingA - Multi-BIOS Chips. This is your actual firmware that controls the Basic Input/Output System. High-end boards (like this one) have multiple BIOS chips in the event of a flashing failure.
B - 7 Segment Displays are used for displaying POST (Power-On Self-Test) error codes. If the system fails during boot, this will show an LED error code to aid in troubleshooting. Not all boards have a Segment Display.'>SATA & USB3.0 Header
Simply enough, this is where SATA and front-panel USB3.0 (in blue) connect to the board. A high-end board with more SATA connections than the chipset allows will utilize a separate SATA comms chip.
'>Chipset / Bridges / PCHThere are a lot of names for what lives under this heatsink, but at the end of the day, it's a chipset. AMD began unifying the North & South Bridges several years ago, but Intel soon followed suit and created the Platform Controller Hub (PCH).
This is dictates the amount of additional lanes available to PCI-e, which firmware / BIOS settings are unlocked (like overclocking), and effectively serves as the communications hub of your PC. Almost all I/O goes through the chipset at some point.
We've written several chipset articles. Check the resources for more info.
'>Troubleshooting Tools aid in system diagnostics when overclocking or failing to POST. Some boards, like this one, feature voltage check stations that allow for hands-free voltmeter probing.This gives a more precise, to-the-second reading on exact vCore (and other) voltages. Next to the voltage station is a set of buttons for switch-less booting and automated overclocking.
'>Voltage Regulator ModuleApplication Of Mosfet
Be sure to check the full article for more specifics on how a VRM works.
A - Capacitors have a capacitance rating, and retain and clean power delivered to the CPU. Higher-quality capacitors are more leak-resistant, making them less prone to failing unexpectedly.
B - Chokes come in many types. This board uses Super Ferrite Chokes (see also: Periodic table). The chokes on the board can often be counted to reveal the number of phases -- 8+2 phase power design will correlate to 8 chokes flanking the CPU. Power is physically stepped-down through these (and the MOSFET/caps), converting it to a more usable supply.
C - MOSFETs & Sink. The MOSFETs (Driver MOS, on this board) are a crucial component of power phasing, using logic gates to gradually clean and step-down what becomes vCore. The MOSFETs are under the heatsink.'>Consumer advice: Keep the plastic cover from your motherboard. You'll need it to RMA the board in the event of a failure.'>(Quick shout to friend of the site Matt Geiger for assisting in the brainstorming for diagram layout).
What is a VRM? Chokes, MOSFETs, and Capacitors Explored
At a top-level, a Voltage Regulator Module (and its backing components) is responsible for cleaning the power / voltage delivered to different electrical components. Let's look specifically at how a VRM interacts with a CPU and motherboard.
The average CPU has a specified operating voltage of somewhere in the 1.1v-1.3v range, +/- a quarter to allow for over- and underclocking. Any more than 1.3v on the average, modern desktop CPU begins to threaten the endurance of the silicon, but improves short-term stability under extreme overclocks. The power supply delivers 12v power to the board for use in the CPU, but in order for this source of power to be usable, the board must step-down the supplied voltage to a more usable output for the CPU (1.2-1.3v, for instance). This is done by phasing the power.
In the process of stepping down the voltage, the phases through which the power is passed will help clean the supply, reducing chances for vDroop (voltage drops). A voltage drop is when the voltage drops below the user-specified vCore setting; if vDroop happens when overclocking at stability-threatening frequencies, the system might exhibit BSODs or other crashes and disabling errors.
About as basic as it gets: This is a VRM designed for a generic circuit. Features MOSFETs, an IC, caps, and chokes. Image from Wiki Commons.
So by cleaning the power more times (by sending it through more phases), we can reduce the risk of vDroop and improve overall stability at extreme frequencies. More on this in a moment. Voltage Regulator Modules are by no means computer-specific; they can be found in any microprocessor-equipped electronic device dealing with power phasing and voltage cleaning (radios, TVs, cars). The composition of a VRM remains the same across all these applications, as discussed below.
What Makes Up A VRM?
I think there's some misconception that the VRM is an independent, self-contained component on the board or in its host device. In actuality, 'VRM' is a term used to collectively describe the composition of MOSFETs (and Driver ICs), capacitors, and chokes, which are used in unison to accomplish the power phasing objectives. To re-iterate in list form, a VRM is made up of:
MOSFETs, or Metal-Oxide Semiconductor Field-Effect Transistors, are responsible for the actual amplification and switching of signals and assist in voltage identification when communicating with the CPU. The CPU tells the MOSFET the requested voltage, and the MOSFET uses a series of logic gates to assist in delivering that voltage (from the 12v supply).
There are several variations on high-end MOSFETs for overclocking, but most of them work in a similar manner. Here's an image from Gigabyte that shows the modern take on driver MOSFETs:
As shown above, most motherboard manufacturers (in high-end boards, at least) now mount the driver IC and two MOSFETs on a single chip. This reduces overall surface area used on the board and has thermal and power advantages.
This image shows ASUS' EPU in action, which is another take on driver MOSFETs. As you can see, the EPU communicate with the CPU to achieve a VID (Voltage ID), which is then used to achieve the correct voltage during the phasing process.
How Does a VRM Work? What does a VRM do?
A VRM physically phases down the higher-voltage supply into a usable voltage for the CPU. The power supplied through the 8/4-pin power connector on the board feeds the CPU. This power is fed through the phases on the board until it eventually gets to the processor, which receives it at the stable, lower voltage.
If you have 8 CPU phases on the board, the power will be voltage-checked eight times before being supplied to the CPU (the power is stepped to the correct voltage in each phase, then checked); similarly, a 12-phase board will step down the power to the same voltage, but because we're passing the supply through more phases, voltage drops can be more gradually controlled, thus creating a cleaner supply of power to the CPU that is more stable.
When shopping for motherboards, you'll likely run across the phase power design terminology in marketing text. This is the specification that describes the number of phases dedicated across the board and to all components. Phase power design is often listed as 4+1, 6+2, 8+3, etc. The number preceding the plus sign (4, 6, and 8 in those examples) is indicative of the number of phases dedicated to the CPU, thus a 6+2 phase power design will dedicate 6 phases to cleaning CPU power. The number after the plus is for other components, often RAM or HT (HyperTransport) for AMD. Just like the CPU, more phases to RAM will help control voltage supply and allow for greater overclocking, but the RAM phases are significantly less impactful than the CPU phases.
As a general rule, you can count the number of chokes flanking the socket to determine the CPU power phases. Eight chokes, in the instance of our MSI board in the video, corresponds to the 8+X phase power design.
'What's the 'Best' VRM Solution? What do I look for?'
We've answered this question in our 'picking the best gaming motherboard' article, but I'll revisit it very briefly here.
When we're looking strictly at the VRM and ignoring all other board components, we're mostly looking for high-quality caps, chokes, and heatsinks for the MOSFETs. I'll start off by saying that anyone uninterested in overclocking needn't worry about the number of phases or the same level of quality components as overclockers. You'll be fine on more simplistic phase power designs and with lower-quality components, since you won't be putting them through as much abuse.
As far as caps go -- and we've got another video coming with specifics -- it's important to opt for leak-resistant capacitors. These are often branded as 'Japanese Capacitors,' 'Dark Capacitors,' 'Solid Capacitors,' 'Hi-C caps,' or 'Military-Class Components.' Electrolytic capacitors are responsible for containing power (a capacitance), and as the capacitor ages, it'll become prone to capacitor aging and decay. As the capacitor decays, it loses its ability to retain power and eventually introduces instability to the system or renders the host device useless. Capacitors can easily be replaced on the board in the event of a failure.
With leak-resistant capacitors, it's highly plausible that the usable life of the system will be exhausted before the capacitor itself needs to be replaced. This improves longevity of the system and its ability to withstand high load.
Then we have chokes. There are different styles of chokes out there, but when looking for a board ready to handle high overclocks, it's a good idea to look for SFCs (Super Ferrite Chokes), Premium Alloy Chokes, or other high-quality chokes. An SFC improves power efficiency and is more stable under higher loads, enhancing the motherboard's ability to step-down power when dealing with overvolting and overclocking.
Here's a look at Gigabyte's setup, showing the MOSFET (top left chip) and Ferrite Core Chokes (the bricks that line the heatsinks).
MOSFETs and heatsinks go together. MOSFETs are often located underneath the heatsinks flanking the CPU socket, given their propensity to rapidly increase in thermal output as the MOSFET continues to phase-down the voltage. When dealing with any sort of power conversion, significant thermal output is the byproduct of the conversion (the energy has to go somewhere). In order to continue operating under load, we need to dissipate that heat rapidly -- this is done with copper heatsinks.
The MOSFET itself is also important. There are different types of MOSFETs, and you've probably noticed that a lot of high-end boards from ASRock, MSI, ASUS, and Gigabyte utilize different terminology for their take on it. DrMOS (Driver MOSFET) is used by MSI and ASRock, ASUS uses an EPU (Energy Processing Unit, which we talked about here), and Gigabyte uses PowerMOS/DES MOS and other solutions. At the end of the day, it all comes down to how well the MOSFET solution can dissipate heat and perform under intense loads. All of these solutions are good at different aspects of either energy preservation or overclocking, so do some research on each prior to making a decision.
If you're just buying for a mid-range machine and aren't too concerned with overclocking (but might play around with it), the selection isn't worth spending a large amount of time researching. Extreme OCs are more volatile, though, so care should be taken when buying.
Continue on to Page 2 to learn about the chipset and PCI-e functionality.
N Type Mosfet Symbol