# What do voltage limits on MOSFETs mean?

I want to include a MOSFET in a schematic I'm designing. I want to manufacture the finished board at JLCPCB, but it seems they they have a very limited set of options for MOSFETs or transistors in general.

This is a part of my schematic:

I want to turn on 4 LEDs with an Arduino. I tried doing this without a MOSFET but the output-wattage of about 2 W is way too low for driving all my LEDs (250 mW each). Here is the datasheet of the MOSFET I chose for now.

I'm not sure if this MOSFET suits my needs. The input to the gate (C01) comes from the Arduino, so 5 V. The VCC would be the same power adapter as the Arduino, so also 5 V, but with way more current available. Each LED would consume 20 mA of current according to the datasheet.

Would the AO3414 be suitable for this? The datasheet states it can handle 20 V, but I'm not sure if that means it can handle 5 V as well? The voltage from gate to source is ±8 V. Is 5 V still possible? If not, could you maybe suggest another MOSFET? If the voltage from gate to source is below 5 V, what would happen if I'd use 5 V anyway?

Edit: I changed the orientation of the MOSFET, would this setup work:

Edit: Since PStechPaul pointed out that the voltage drop is too much, I gave each LED a resistor. Would it be OK this way:

I calculated the resistance with this calculator.

• 20V is a maximum, as is 3A. Because 5 < 20, this is a safe application. Also notice Vgs(on) at Rds(on) is given for 4.5, 2.5 and 1.8V. This means it will also turn on strongly (at least up to the current listed there) even as low as 1.8V. 5 > 1.8 so it will be well turned on. Any Vgs(on) from 1.8 to 8V will do the trick, it would seem. Remember to add a pull-up resistor so the gate voltage is defined during reset/boot (before pin states have been assigned). Jul 24, 2022 at 7:14
• Not what you asked about but why not bog-standard low side MOSFET? It will greatly simplify your driving requirements. Jul 24, 2022 at 7:30
• @TimWilliams please note that the OP is proposing to put an N-channel mosfet on the high side. So I don't think the schematic as shown is correct. It will not result in the mosfet being turned on. Jul 24, 2022 at 7:43
• I see that your white LEDs have a forward voltage of 2.6 to 3.6 volts. So you can't use two in series with a 5V supply. Jul 24, 2022 at 8:12
• Could you explain what you mean by "output wattage"? The power rating of a transistor rarely matters when just using it as a switch, if that's what you mean. That refers to how much power can be safely dissipated in the transistor, not how much power it can switch. Jul 24, 2022 at 13:56

simulate this circuit – Schematic created using CircuitLab

That MOSFET will work fine but you should put it on the low side between the LEDs and GND. Not only was it upside down (source/drain swapped) but it was also on the high side of the load when it should be on the low side of the load. After you build it, you can fine-tune the LED current by adjusting R1-R4. If the current is too high, use a larger resistor. If the current is too low use a smaller resistor.

Hope that helps.