IRLZ44N PCB Design Guide: Footprint, Pinout, and Alternatives
55 V 47 A logic-level N-channel MOSFET for hobby power switching
The IRLZ44N is the through-hole workhorse of hobby power switching: a 55 V, 47 A logic-level N-channel MOSFET in TO-220AB that turns LED strips, heaters, pumps, and motors on and off from a microcontroller pin. It is a legacy International Rectifier design now sold by Infineon — the current orderable part number is IRLZ44NPBF, the lead-free version — and it remains in active production.
"Logic level" deserves a precise reading. The datasheet guarantees RDS(on) at VGS = 5.0 V (25 mΩ max) and also characterizes 4.0 V (35 mΩ max); there is no 3.3 V specification at all. Driven from a 5 V Arduino it is fully enhanced and barely warms up at tens of amps. Driven from a 3.3 V ESP32 or Pi pin it is only partially enhanced, and whether it survives your load current is a question for the transfer and output curves, not the headline numbers.
Beyond gate drive, the recurring IRLZ44N mistakes are hardware classics: substituting the standard-gate IRFZ44N, forgetting that the mounting tab is the drain, PWM-ing a 48 nC gate straight from a GPIO, and using a modern trench FET as a linear regulator. Each is covered below.
What breaks boards
Logic level means 5 V — 3.3 V drive is not specified
RDS(on) is guaranteed at VGS = 5.0 V (25 mΩ max at 25 A) and 4.0 V (35 mΩ max at 21 A). At 3.3 V the part is only partially enhanced: threshold spans 1.0–2.0 V, and the usable current at 1.3 V above a worst-case threshold comes from the transfer characteristic, not the ratings table. A 3.3 V-driven IRLZ44N passing a few amps often works on the bench with a typical part and cooks in the field with a corner one. From 3.3 V rails, verify against the curves or pick a FET specified at 2.5 V.
IRLZ44N is not IRFZ44N
The single most common substitution error. The IRFZ44N is the standard-gate sibling and needs about 10 V of gate drive to reach its rated on-resistance; at 5 V logic drive it half-conducts and burns up under load. The one-letter difference — L for logic level, F for standard — decides whether the FET works from an MCU pin at all. Check the reel and the invoice, not just the schematic.
The TO-220 tab is the drain
The mounting tab is electrically common with the drain (pin 2). In a low-side switch that means the tab sits at the load's switched node, not ground — bolt it to a grounded heatsink and you have a short. Use an insulating pad and shoulder washer, or float the heatsink and keep fingers and chassis away from it.
PWM heat is switching loss — mind the 48 nC gate
Total gate charge is 48 nC max, and a bare GPIO sourcing 20-odd mA takes microseconds to slew it, leaving the FET in its linear region every edge. At low PWM frequencies this is survivable; at tens of kHz and amps of load it is the classic "logic-level FET runs hot on PWM" complaint. Use a gate resistor sized for your driver, and above a few kHz at high current use a proper gate driver so edges are fast.
Linear (analog) operation is an SOA trap
Modern trench FETs like this one have poor DC safe-operating-area compared with old planar parts — holding the gate half-on for analog dimming or constant-current duty concentrates dissipation and invites thermal runaway hot-spotting. Treat the IRLZ44N as a switch: fully on or fully off. For linear current control, use a part characterized for DC SOA or a proper linear regulator stage.
Inductive loads still need a flyback diode
The body diode sits from source to drain and does nothing to clamp the inductive kick of a relay coil or motor when the FET turns off — the drain simply flies above the 55 V rating. Put a flyback diode across the load itself. The body diode is a freewheeling path in bridge topologies, not a substitute for a clamp in a low-side switch.
Key specifications
| Parameter | Value | Source |
|---|---|---|
| VDS | 55 V (VDSS; V(BR)DSS min 55 V at VGS = 0 V, ID = 250 µA) | PD-94831 datasheet, page 1 header and Electrical Characteristics |
| ID | 47 A continuous at TC = 25 °C (VGS = 10 V); 33 A at TC = 100 °C; 160 A pulsed | PD-94831 datasheet, Absolute Maximum Ratings |
| RDS(on) | 25 mΩ max at VGS = 5.0 V, ID = 25 A (22 mΩ max at VGS = 10 V; 35 mΩ max at VGS = 4.0 V, ID = 21 A) | PD-94831 datasheet, Electrical Characteristics, RDS(on) |
| VGS(th) | 1.0 V min / 2.0 V max (VDS = VGS, ID = 250 µA) | PD-94831 datasheet, Electrical Characteristics |
| Qg (total gate charge) | 48 nC max (ID = 25 A, VDS = 44 V, VGS = 5.0 V) | PD-94831 datasheet, Electrical Characteristics |
| Package / tab net | TO-220AB; mounting tab = drain | PD-94831 datasheet, page 1 and package outline |
Verified against the manufacturer datasheet on 2026-07-09. Confirm the current revision before production use.
Alternatives
- IRLB8721 — better enhancement at 4.5 V and lower gate charge, at a 30 V rating — often the stronger choice for 5 V-driven loads below 30 V.
- AO3400A — SOT-23 SMD for small loads up to a few amps — the right size when a TO-220 is overkill.
- FQP30N06L — another through-hole logic-level 60 V FET filling the same socket; check stock and price, and verify its gate-drive curves the same way.
Common questions
- Can I drive an IRLZ44N from a 3.3 V GPIO?
- Only with care. The datasheet specifies RDS(on) at VGS = 5.0 V and 4.0 V, not 3.3 V, and the threshold can be as high as 2.0 V — at 3.3 V the FET is partially enhanced. It may pass an amp or two acceptably, but verify against the transfer curves; for 3.3 V designs a FET specified at 2.5 V gate drive is the safer pick.
- What is the difference between the IRLZ44N and IRFZ44N?
- The gate. The IRLZ44N is logic level, with on-resistance guaranteed at 5 V gate drive; the IRFZ44N is standard gate and needs roughly 10 V to enhance fully. Substituting the F part into a 5 V MCU circuit gives a half-on FET that overheats under load.
- Why does my IRLZ44N get hot with PWM?
- Switching loss. With 48 nC of gate charge, a bare GPIO slews the gate slowly, so the FET spends every edge in its dissipative linear region. Add a properly sized gate resistor, and above a few kHz at high current use a dedicated gate driver. Conduction loss at DC is tiny — 25 mΩ max at 5 V drive.
- Is the IRLZ44N tab connected to a pin?
- Yes — the TO-220AB mounting tab is electrically common with the drain. In a low-side switch the tab carries the switched node, so a heatsink must be isolated with a pad and shoulder washer, or left floating and kept clear of chassis and other conductors.