I see many people recommending this MOSFET IRF634 to drive LED. My question is this: in the datasheet it says VGS = 10 but arduino can send only 5v. So why do people recommend this mosfet if it can never be saturated using arduino?


I need to buy a mosfet (probably a logic one) which can be driven by arduino 5v pin. My output will be at most at 20v and 3 amps, nothing more than that. So which mosfet should I use from this list:

There are 4 pages at the bottom (1 2 3 4) and I would like to know which is the best MOFEST that they provide and I can buy. This store is in a neibourghood close to me so I can go there and buy it, better than buy online but the owner does not know how to choose the best mosfet for this case.

Could you please help me? I already bought the BUK95/9607-30B and it's good but it's too overkill for what I need.

OBS: I dont want a transistor, I want a mosfet which is much easier to drive, dont need to calculate base resistor or anything like that.

I have not seen others recommending it, however, you are correct with your question. I would not use it without some sort of external gate drive. What you want is a logic level FET - there are many out there that 5v will turn on very nicely. If you are using a 3.3v circuit then your options are more limited since most of the FETs that turn on at 3v seem to be SMD devices.

Actually, you should have a gate resistor to limit the drive current from the Arduino since the gate has a fair amount of capacitance. You should also have something like a 10k from the drive pin on the Arduino to ground so that when the drive pin first powers up in an input mode or is floating, the gate of the FET is turned off until the Arduino is configured to drive the gate correctly.

@gpsmikey great explanation, I never used a resistor in the gate and never connected it to ground and it’s a good idea.

But from that list in the link, do you know which mosfet is logic?

Some people recommend this mosfet online in many tutorials but I am glad at least someone came to the same understanding as me that the voltage provided by arduino will not be enough to drive this mofest fully.


The owner does not know anything about these mosfets, he only resells them.

If you cant spare a time to see the list and recommend me one, could you tell me the 2 or 3 most popular logic MOSFETS that can go up to 20V and 3A?

AOI508, AOI510

From your list,
IRLF44 and then IRLZ34 look to the best choices. Read their specs at
You may need a small heatsink as well. Pdissipated = I x I x R = 3A x 3A x .04ohm = 360mW.

batata004: OBS: I dont want a transistor, I want a mosfet which is much easier to drive, dont need to calculate base resistor or anything like that.

For what it's worth - the "T" in MOSFET stands for "Transistor" - MOSFETs are just a type of transistor. What you probably meant was you did not want a standard bipolar transistor. Also (at least with International Rectifier numbers), an "L" in the part number often indicates it is a Logic level - for example the IRF520 is a standard MOSFET, but the IRL520 is a Logic level version (fully on with a gate voltage of 5v).

@CrossRoads I went to the store right now and bought one IRLZ34 and one IRLF44. I tested it right now and for some reason the IRLF44 does not make my LED as bright as the IRLZ34. Maybe the IRLZ34 logic level is not 5v, maybe it's higher? Anyway, I really appreciate your help, now I have 2 good mosfets.

Would you mind telling me if this MOSFET BUK95/9607-30B (datasheet at ) is better than IRLZ34and IRLF44 in terms of efficiency?

I usually use IRF520, IRF530, IRF630 or similar (depending on price and availability), when I need a switching MOSFET in TO-220 package. They work great at logic levels with 1-2kOhm series resistor between the logic output and the MOSFET gate, and a 50-100kOhm pull-down on the MOSFET gate.

BUK9507-30B: RDSon drain-source on-state resistance: @ VGS = 5 V; ID = 25 A; 5.9 typical, 7 max mΩ

That'd be pretty good also: At 3A, P = 3A x 3A x .0059 ohm = 53mW

IRLZ34, Rds = .05 ohm @ Vgs = 5V IRLZ44, Rds = .028 ohm @ Vgs = 5V The '44 should be brighter.

I can't find IRLF44.

Thank you again @CrossRoads I understood everything you said. Would min just telling me if I should always use a resistor in the logic pin connecting my arduino to the login pin in the mosfet? When using a “normal” transistor I know I need to carefully choose this resistor because of the “gain stuff”, but with a MOSFET should I still use a resistor? If so, how can I determine the value?

I always use a resistor as the Gate of a MOSFET looks like a capacitor to the Arduino - if you read the datasheet you will see a value for Gate capacitance. I use a resistor that allows a lot of current flow to charge/discharge that capacitor quickly to turn fully off and on quickly. 5V/25mA = 200 ohm, so 180, 200, 220 are all good. I add a 10K to Gnd on the MOSFET side to keep the part off during Arduino reset when all pins are Inputs and the levels just floating around.

@CrossRoads I appreciate your patience with me into my questions but your last answer raised many more questions.

First, you said you use a resistor as a capacitor. Do I really need a capacitor or a resistor at the gate? I mean, not using it will destroy my arduino pin?

Second, you say you added a resistor in the GND pin, it should be a really realy big resistor, right? I mean, a 100000w resistor? Cause if in that mosfet is flowing 5 amps (for example), the power would be R*I^2 = 10000 * 25 = A LOT! Probably I didnt understand something...

What I said was that the Gate pin of the MOSFET looks like a capacitor.
An Arduino trying to drive a capacitor from Low to High, or from High to Low, can output a lot of current. Putting a resistor between the Arduino and the Gate capacitance limits the Arduino current.

10000 Ohm resistor (10K) bleeds off any charge on the Gate capacitance when the Arduino is not driving its output high or low.

The Source pin of the N-Channel MOSFET connects to Gnd only.

The attached shows a couple of examples. The NPN transistor can be replaced with the N-channel MOSFET.
Relay and MOSFET connections, LEDs.jpg

Great, I think I understood :) But do you think I could damage an arduion pin without using the resistor in the gate?