PWM LED strip dimmer
Low-side switching a single-color 12V LED strip with an Arduino PWM pin. The IRLZ44N is the community-standard FET for this because 5V drive fully enhances it and its low RDS(on) keeps it cool at strip currents.
IRLZ44N MOSFET
Logic-level N-channel HEXFET power MOSFET that switches up to 47A at 55V and turns fully on from a 5V gate.
What is the IRLZ44N MOSFET?
The IRLZ44N is a logic-level N-channel power MOSFET in a TO-220AB package. Its defining feature is that on-resistance is specified with only a 5V gate drive (0.025 ohm at VGS=5V, ID=25A), so a 5V microcontroller or logic output can switch it fully on without a dedicated gate-driver chip. It handles 55V drain-to-source and 47A of continuous drain current at 25C (33A at 100C), which makes it a common choice for switching high-current loads from a small logic signal.
Electrically it behaves as a voltage-controlled low-side switch. The gate threshold (VGS(th)) sits between 1.0V and 2.0V, but full enhancement and the lowest on-resistance are only reached near 4-5V, which is exactly why it is marketed as logic-level. The very low RDS(on) means it dissipates little heat at moderate currents, and an integral body diode conducts from source to drain. The gate looks like a small capacitor (total gate charge about 48nC, input capacitance around 1700pF), so it draws current only during switching transitions.
In practice the IRLZ44N is used to turn high-power loads such as DC motors, pumps, fans, heaters, solenoids, and LED strips on and off (or PWM them) from an Arduino or similar board. Because it is an N-channel device driven from ground, it belongs on the low side of the load. Note that 3.3V logic does not fully enhance it, so it is best paired with 5V drive when switching significant current.
IRLZ44N MOSFET pinout
| Pin | Function | Type |
|---|---|---|
S Source | Passive | Passive |
G Gate | Analog | Digital input |
D Drain | Passive | Passive |
Specifications
- Dimensions
- 4.5 × 4.5 × 3.5 mm
Verified from the Tinkered component library.
Circuit requirements
- Wire it as a low-side switch: the load goes between the positive supply and the Drain, the Source connects to ground, and the Gate is driven by the microcontroller pin. The load supply ground and the microcontroller ground must be common.
- Add a small series gate resistor (roughly 100-470 ohm) between the driving pin and the Gate to limit the inrush current into the gate capacitance during switching and protect the driving pin.
- Add a 10k ohm pulldown resistor from Gate to Source (ground). This keeps the gate defined low while the microcontroller is resetting or booting so a floating gate does not switch the load on unexpectedly.
- Drive the gate at 5V for lowest on-resistance. It is fully specified at VGS=5V (0.025 ohm) and still conducts well at 4V, but at 3.3V it is only partly enhanced, giving higher RDS(on) and more heat, so it is not ideal for high current straight off a 3.3V pin.
- Never exceed the VGS gate-to-source limit of plus or minus 16V. When the control signal comes from a higher voltage than 16V, use a resistor divider or a proper gate driver.
- For inductive loads (motors, relays, solenoids) add a freewheeling/flyback diode across the load to clamp the turn-off voltage spike. The part is avalanche rated, but external clamping is still best practice.
- The metal mounting tab is electrically connected to the Drain, not to ground. If you bolt it to a grounded heatsink or chassis, use an insulating pad and shoulder washer so you do not short the drain.
Common IRLZ44N MOSFET mistakes
Assuming 3.3V fully turns it on
The threshold voltage is only 1-2V, so the part starts conducting at low gate voltage, but the rated 0.025 ohm on-resistance needs about 5V. At 3.3V the channel is only partly open, so it runs hot at high current. Use 5V drive, a gate driver, or a true 3.3V logic-level FET.
Leaving the gate floating
A MOSFET gate is high impedance. If the only thing on the gate is the microcontroller pin, it floats during reset or power-up and the load can flicker or switch on by itself. Always add a pulldown resistor (around 10k) from gate to ground.
Using it as a high-side switch
An N-channel MOSFET needs its gate above its source to turn on. On the high side the source sits at the load voltage, so a 5V logic pin cannot switch it. Put it on the low side (source to ground) or use a dedicated high-side driver.
Bolting the tab to ground
The TO-220 tab and heatsink pad are internally connected to the Drain, not the Source. Mounting it directly to a grounded chassis or shared heatsink shorts the drain. Use an insulating thermal pad and bushing when the heatsink is grounded or shared.
Switching an inductive load without a flyback diode
Motors, relays, pumps, and solenoids generate a large voltage spike when the FET turns off. Without a freewheeling diode across the load, that spike stresses the MOSFET and can couple back into the microcontroller.
Popular IRLZ44N MOSFET projects
Motor, pump, or fan on/off and speed control
Turning a 12V DC motor, water pump, or fan on and off (or PWM speed control) from a microcontroller, with a flyback diode across the load to absorb turn-off spikes.
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Build with the IRLZ44N MOSFET.
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