Parts

IRF520 MOSFET: pinout, ratings, and gate drive from Arduino

By Bulan Sarkar

The IRF520 is G-D-S: with the printed face toward you and the leads down, gate, drain and source run left to right, and the metal tab is also the drain. It is a 100 V, 9.2 A N-channel MOSFET in a TO-220. Its data sheet gives the on-resistance at one gate voltage only, 10 V, and allows a threshold as high as 4 V. That makes it a poor match for the 5 V Arduino pin that the popular "IRF520 MOSFET driver module" is sold to work with, and a 3.3 V pin leaves it off.

This page reads Vishay's IRF520 data sheet (document 91017) and Infineon's IRF520N, which is a different, later part under a similar number. It works through a 12 V, 1 A load at 10 V and at 5 V on the gate, with the heat in each case, and shows the parts to use instead when a microcontroller drives the gate directly.

Datasheet: Vishay Siliconix IRF520 Power MOSFET, document 91017 (PDF)

Pinout by package

IRF520 TO-220 · Vishay1=G 2=D 3=S

Printed face toward you, leads down: gate, drain, source from left to right. The tab is the drain.

The tab is the drain. On a shared or grounded heatsink it needs an insulating pad.

Source: Vishay Siliconix IRF520 Power MOSFET, document 91017, p. 1 (TO-220AB drawing with the leads labelled G, D, S); Vishay Siliconix IRF520 Power MOSFET, document 91017, p. 2 (thermal table: junction-to-case resistance measured to the drain)

IRF520N TO-220 · Infineon1=G 2=D 3=S

Printed face toward you, leads down: gate, drain, source from left to right. The tab is the drain.

Source: Infineon IRF520NPbF data sheet, p. 1 (symbol labelled Gate pin 1, Drain pin 2 and tab, Source pin 3; G D S table); Infineon IRF520NPbF data sheet, p. 8 (TO-220 outline with leads numbered 1, 2, 3)

Which one do you have?

Read the print on the face. IRF520 with no letter is the original part, made today by Vishay (the sheet on this page) and by others; Vishay calls it a third-generation MOSFET. IRF520N, from Infineon (formerly International Rectifier), is a fifth-generation design with the same pins and voltage. It has a lower on-resistance, 0.20 Ω against 0.27 Ω, a higher gate charge limit and a smaller avalanche rating. A PbF suffix only means lead-free.

The blue "IRF520 MOSFET driver module" is a small board with the MOSFET, a screw terminal for the load and header pins for the signal. Unless your board carries a gate driver or a transistor stage, the gate sees the signal pin's own voltage: 5 V from an Uno, 3.3 V from an ESP32. The numbers below show what the MOSFET does at those voltages.

Absolute maximum ratings

The two makers agree on 100 V drain to source and ±20 V on the gate. They differ on the rest. Vishay rates 9.2 A and 60 W with the case at 25 °C, Infineon 9.7 A and 48 W, and Vishay's avalanche rating is more than twice Infineon's. If a part may come from either maker, design to the lower figure in each row.

Absolute maximum ratings and thermal data, from each maker's data sheet
Parameter	IRF520TO-220	IRF520NTO-220
Drain-source voltage VDS	100 V	100 V
Gate-source voltage, max VGS	±20 V	±20 V
Continuous drain current IDcase at 25 °C, VGS 10 V	9.2 A	9.7 A
Continuous drain current IDcase at 100 °C, VGS 10 V	6.5 A	6.8 A
Pulsed drain current IDM	37 A	38 A
Power dissipation PDcase held at 25 °C, not free air	60 W	48 W
Single-pulse avalanche energy EAS	200 mJ	91 mJ
Junction to case, max RthJC	2.5 °C/W	3.1 °C/W
Case to sink, typical RthCSflat, greased surface	0.50 °C/W	0.50 °C/W
Junction to air, max RthJAno heatsink	62 °C/W	62 °C/W
Junction temperature TJ	−55 to +175 °C	−55 to +175 °C

The 9.2 A and 60 W need the case held at 25 °C, which no real heatsink does. In free air the part has 62 °C/W from junction to air. At 10 V on the gate our MOSFET guide puts the most it can carry without a heatsink at about 1.5 A, for a junction 60 °C above the room.

Characteristics: one gate voltage, and a high threshold

At 25 °C. Limits are guaranteed unless marked typical; the 5 V drain current row is read from each maker's typical curve.
Parameter	IRF520TO-220	IRF520NTO-220
Gate threshold voltage VGS(th)VDS = VGS, ID = 250 µA	2.0 to 4.0 V	2.0 to 4.0 V
On-resistance, max RDS(on)VGS = 10 V (ID 5.5 A Vishay, 5.7 A Infineon)	0.27 Ω	0.20 Ω
On-resistance at 5 V or 4.5 V gate RDS(on)	not specified	not specified
Forward transconductance, min gfsVDS = 50 V (ID 5.5 A / 5.7 A)	2.7 S	2.7 S
Total gate charge, max QgVGS = 10 V, VDS = 80 V	16 nC (ID 9.2 A)	25 nC (ID 5.7 A)
Input capacitance, typical CissVGS = 0 V, VDS = 25 V, 1 MHz	360 pF	330 pF
Reverse transfer capacitance, typical CrssVGS = 0 V, VDS = 25 V, 1 MHz	34 pF	54 pF
Drain current, typical IDVGS = 5 V, VDS = 50 V, 25 °C (Fig. 3, read by us)	about 2 A	about 4.4 A
Body diode forward voltage, max VSDTJ = 25 °C (IS 9.2 A / 5.7 A)	1.8 V	1.3 V
Body diode reverse recovery, typ / max trrdI/dt = 100 A/µs	110 / 260 ns	99 / 150 ns

The line that matters is the on-resistance row. Both sheets give a maximum at 10 V on the gate and at no lower voltage. The threshold, 2.0 to 4 V, is the gate voltage at which the part passes just 250 µA, so a part with a 4 V threshold is barely starting to conduct at 4 V.

Figure 1. Threshold range (grey) and every gate voltage with a guaranteed on-resistance (green). The IRF520 and IRF520N have one point each, at 10 V; the logic-level IRLZ44N has three.

The typical curves show what happens below 10 V. Vishay's Fig. 3 plots drain current against gate voltage for a typical part at 50 V across it: about 1 A at 4.5 V, about 2 A at 5 V, and close to 19 A at 10 V. Infineon's IRF520N curve sits further left, about 4.4 A at 5 V. Those are the most a typical part will pass at that gate voltage, however low the load resistance. A part with a higher threshold passes less.

Figure 2. Typical transfer curves, read by us from each maker's Fig. 3 (25 °C, 50 V across the part), and the Vishay curve moved right to the 4 V threshold limit. At 5 V a typical IRF520 just clears a 1 A load; a high-threshold part does not.

What it is good for

Low-side switching of solenoids, lamps, small motors and LED strips up to about 1.5 A without a heatsink, when something drives the gate to 10 V or more: a gate driver, a 12 V rail through a transistor stage, or a 555 running from 12 V.
Circuits above 30 V. At 100 V it has more headroom than the 55 V logic-level parts, for 24 V and 48 V loads.
Repairs, where an existing board was designed around it and already drives the gate properly.

It is the wrong part to hang straight off a microcontroller pin. For that, see IRFZ44N vs IRLZ44N and our guide to choosing a MOSFET for Arduino and ESP32.

Worked example: a 12 V, 1 A solenoid at 10 V and at 5 V on the gate

A 12 V solenoid whose coil measures 12 Ω draws 1 A. The IRF520 switches its low side: source to ground, coil between +12 V and the drain, a diode across the coil. The gate is fed through 220 Ω, with 10 kΩ to ground on the drive side so the gate is held off while the pin floats at reset. We put the pull-down before the 220 Ω so the two do not divide the drive voltage.

Figure 3. The low-side switch from the example, drawn and simulated by our schematic checker. With a typical part it settles at 0.98 A and 0.26 V across the MOSFET at 10 V drive, and at 0.95 A and 0.63 V at 5 V; a part at the 4 V threshold limit holds the coil to 0.68 A. The 1N4007 keeps the drain near 13 V at switch-off.

1. At 10 V on the gate (guaranteed). The data sheet promises at most 0.27 Ω. 1 A × 0.27 Ω = 0.27 V across the part and 0.27 W of heat. On-resistance rises as the die warms, so we multiply by 1.5, the margin our MOSFET guide uses: 0.41 W. With no heatsink, 0.41 W × 62 °C/W = 25 °C above the room, about 65 °C at the junction in a 40 °C room, well clear of the175 °C rating.

2. At 5 V on the gate, a typical part (no guarantee). The data sheet has no row here, so we fitted a curve to Vishay's typical Fig. 3: drain current = 0.679 A/V² × (V_GS − 3.29 V)², with a series resistance that makes it 0.27 Ω at 10 V. At 5 V that part could pass up to 1.99 A; carrying 1 A it drops about 0.67 V. That is 0.67 W, or 41 °C above the room, about 81 °C at the junction. It works and runs warm, and nothing on the data sheet says your part is typical.

3. At 5 V, a part at the 4 V threshold limit. Move the same curve right to a 4 V threshold. At 5 V the part can then pass only 0.68 A, so the coil never reaches 1 A. The drain sits at 12 V − 0.68 A × 12 Ω = 3.85 V, and the part dissipates 0.68 A × 3.85 V = 2.62 W. That is 162 °C above the room, about 202 °C at the junction, past the 175 °C rating. A real part with that threshold is at least this bad, because the 250 µA threshold sits below the point our straight-line fit calls the threshold.

4. At 3.3 V. Our fit puts a typical part's turn-on at 3.29 V, so at 3.3 V it passes 0.07 mA, essentially nothing. Vishay's Fig. 3 does not even start until 4 V. Some low-threshold parts will conduct a little, but no data sheet figure supports using it.

Figure 4. Heat in the IRF520 for the same 1 A load. The same part number at the same 5 V can sit in either of the bottom two bars.

A diode across the coil, cathode to +12 V, is not optional with a solenoid, relay or motor; see the flyback diode. The gate drive lesson covers ways to get 10 V onto the gate from a logic pin.

Worked example in numbers

10 V gate, 1 A: 0.41 W
Junction, 10 V gate: 65 °C
5 V gate, high threshold: 0.68 A
Heat in that case: 2.62 W

Tips and checks

Measure drain to source with the load running. A few tenths of a volt at 1 A is right; a volt or more means the gate is not driven hard enough.
If an IRF520 module gets hot at a load well under its 9.2 A, the gate voltage is the cause. Swap in a logic-level MOSFET of the same pinout or drive the gate from a higher rail.
Keep the 10 kΩ pull-down. A floating gate can leave the part half on, and half on is where it gets hottest.
Check the tab before power goes on. It is the drain, and on a grounded heatsink it shorts the load. Use an insulating pad and shoulder washer, then meter for an open circuit.
For PWM, the gate charge matters more than the gate resistor. Vishay's 16 nC maximum through 220 Ω is fine at a few kHz; at tens of kHz use a gate driver.

Substitutes

The IRF520N and IRF540N drop in where the gate already gets 10 V. Where a 5 V pin drives the gate, the IRLZ44N is the fix, provided the load supply is under its 55 V rating.

Pin order read with the printed face toward you, leads down, left to right (TO-220)
Part	Pins	Verdict
IRF520N	G-D-S	Drop-in at a 10 V gate: same 100 V and ±20 V, lower on-resistance (0.20 against 0.27 Ω). Its gate charge limit is higher, 25 nC against 16 nC. Still not specified at 5 V.Infineon IRF520NPbF data sheet, p. 1; Infineon IRF520NPbF data sheet, p. 2
IRF540N	G-D-S	The bigger brother at a 10 V gate: 100 V, 33 A, 44 mΩ. Same gate problem: threshold up to 4.0 V and resistance given only at 10 V.Infineon IRF540NPbF data sheet, p. 1; Infineon IRF540NPbF data sheet, p. 2
IRLZ44N	G-D-S	The fix for a 5 V pin, if the load runs from 55 V or less: on-resistance guaranteed at 5 V (25 mΩ) and 4 V. Its gate only takes ±16 V.Infineon (International Rectifier) IRLZ44NPbF data sheet, PD-94831, p. 1; Infineon (International Rectifier) IRLZ44NPbF data sheet, PD-94831, p. 2; Infineon (International Rectifier) IRLZ44NPbF data sheet, PD-94831, p. 8

Checking one with a multimeter

Short all three leads together for a moment to empty the gate. Set the meter to diode test.
Red probe on the source, black on the drain: the body diode reads about 0.4 to 0.7 V. Reversed, it should read open.
Touch the red probe to the gate with the black on the source for a second. That charges the gate to the meter's test voltage. Now red on the drain, black on the source: a good part conducts. Short gate to source and it goes open again.
If step 3 shows nothing, your meter's test voltage may be below the threshold. That is the same problem as the 3.3 V pin, not a dead part.

The transistor testing lesson and continuity and diode test explain what the meter is doing.

What we'd do

Use the IRF520 only where the gate gets 10 V or more, and keep it under about 1.5 A without a heatsink. If a 5 V Arduino pin drives the gate, use an IRLZ44N in the same footprint, or replace the module with one built on a logic-level part. From a 3.3 V board, use a part rated at 2.5 V on the gate, as the MOSFET guide describes.

Questions people ask

What is the IRF520 pinout?

Gate, drain, source from left to right with the printed face toward you and the leads down. The metal tab is connected to the drain.

Can an Arduino drive an IRF520 directly?

Not reliably. Its on-resistance is only specified at 10 V on the gate and the threshold can be 4 V. A typical part will switch about 1 A at 5 V and run warm; a high-threshold part limits near 0.68 A and overheats.

Does the IRF520 module work with an ESP32?

No. At 3.3 V on the gate a typical IRF520 is barely at its threshold. Use a logic-level MOSFET rated at 2.5 V, or a driver stage that raises the gate voltage.

What is the difference between the IRF520 and the IRF520N?

Same pins, same 100 V and ±20 V. The IRF520N has a lower on-resistance (0.20 Ω against 0.27 Ω), a higher gate charge limit (25 nC against 16 nC) and a lower avalanche rating. Its typical curve passes more current at 5 V, but neither is specified there.

How much current can an IRF520 switch?

The 9.2 A rating needs the case held at 25 °C. Without a heatsink, at 10 V on the gate, about 1.5 A keeps the junction 60 °C above the room. Above that it needs a heatsink, and the IRF540N is the easier part.

Buying the IRF520 in India

Loose IRF520s and the blue module are sold by every Indian electronics shop and most online sellers. Check the print for IRF520 or IRF520N and a maker's logo, and meter a part before it goes on a board. If the job is a 5 V Arduino project, buy the IRLZ44N instead. Our guide to buying electronic components in India compares ten online sellers and covers how to spot fakes.

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Used in these lessons

Lessons that go deeper

Datasheets this page was checked against

Vishay Siliconix, IRF520 Power MOSFET, document 91017 (S21-0819-Rev. C, 02-Aug-2021)
Infineon, IRF520NPbF data sheet (Rev. 2.1, 2026-07-24)
Infineon, IRF540NPbF data sheet (Rev. 2.1, 2026-07-24)
Infineon (International Rectifier), IRLZ44NPbF data sheet, PD-94831 (dated 11/11/03)

Makers revise datasheets. If the copy you download has a newer revision and a number here disagrees with it, the datasheet wins, and we would like to hear about it.