IRLB8721 — 30V 62A Ultra-Low RDS(on) Logic-Level N-Channel MOSFET (TO-220)

Overview

The IRLB8721 (IRLB8721PBF) is an exceptionally popular 30V, 62A N-channel logic-level power MOSFET manufactured by Infineon Technologies (formerly International Rectifier). Housed in a through-hole TO-220AB package, it is specifically optimized for ultra-low on-resistance and minimal gate charge ( $Q_g = 8.4\text{ nC}$ ).

With an $R_{DS(on)}$ of just $8.7\text{ m}\Omega$ at $V_{GS} = 10\text{V}$ and $13.1\text{ m}\Omega$ at $V_{GS} = 4.5\text{V}$ , the IRLB8721 can switch tens of amperes of current with negligible heat generation and without requiring a bulky heatsink. Extensively featured in DIY electronics tutorials (Adafruit, SparkFun) and widely used across the 3D printing community (RepRap, RAMPS controller boards, Ender-3 upgrades) for 12V/24V heated beds, hotend heater cartridges, high-current LED arrays, and brushed DC motor controllers driven directly by 3.3V and 5V microcontrollers.

Quick reference


Transistor Type	N-Channel Logic-Level Power MOSFET
Package	TO-220AB (Pin 1: Gate, Pin 2: Drain/Tab, Pin 3: Source)
Drain-Source Voltage ( $V_{DSS}$ )	$30\text{ V}$ max
Continuous Drain Current ( $I_D$ )	$62\text{ A}$ at $T_C = 25^\circ\text{C}$ ( $44\text{ A}$ at $100^\circ\text{C}$ )
Gate Threshold Voltage ( $V_{GS(th)}$ )	$1.35\text{ V}$ min to $2.35\text{ V}$ max
On-Resistance ( $R_{DS(on)}$ )	$8.7\text{ m}\Omega$ at $10\text{V}$ / $13.1\text{ m}\Omega$ at $4.5\text{V}$
Total Gate Charge ( $Q_g$ )	$8.4\text{ nC}$ typical (Ultra-low gate capacitance)
Total Power Dissipation ( $P_D$ )	$65\text{ W}$ ( $T_C = 25^\circ\text{C}$ )

Terminal identification

text

        ┌─────────┐
        │  TO-220 │
        │ LB8721  │
        └─┬───┬───┬─┘
          1   2   3
          G   D   S

Pin	Terminal	Description
1	`Gate` (`G`)	Gate control input (Connect to MCU GPIO via $100\ \Omega \dots 220\ \Omega$ series resistor)
2 / Tab	`Drain` (`D`)	High-power load switching terminal / Tab (Connect to load negative return)
3	`Source` (`S`)	Source terminal (Connect to Common System Ground 0 V)

Specifications

Parameter	Symbol	Min	Typ	Max	Unit	Conditions
Drain-Source Breakdown Voltage	$V_{(BR)DSS}$	30	—	—	V	$V_{GS} = 0\text{V}, I_D = 250\ \mu\text{A}$
Gate Threshold Voltage	$V_{GS(th)}$	1.35	1.80	2.35	V	$V_{DS} = V_{GS}, I_D = 25\ \mu\text{A}$
On-Resistance ( $V_{GS} = 10\text{V}$ )	$R_{DS(on)}$	—	6.5	8.7	mΩ	$V_{GS} = 10\text{V}, I_D = 31\text{A}$
On-Resistance ( $V_{GS} = 4.5\text{V}$ )	$R_{DS(on)}$	—	9.7	13.1	mΩ	$V_{GS} = 4.5\text{V}, I_D = 25\text{A}$
Gate-to-Drain Charge	$Q_{gd}$	—	3.5	—	nC	$V_{DS} = 15\text{V}, V_{GS} = 4.5\text{V}, I_D = 25\text{A}$
Total Gate Charge	$Q_g$	—	8.4	13	nC	$V_{DS} = 15\text{V}, V_{GS} = 4.5\text{V}, I_D = 25\text{A}$
Turn-On Delay Time	$t_{d(on)}$	—	11	—	ns	$V_{DD} = 15\text{V}, I_D = 25\text{A}, R_G = 3.0\ \Omega$
Turn-Off Delay Time	$t_{d(off)}$	—	11	—	ns	$V_{DD} = 15\text{V}, I_D = 25\text{A}, R_G = 3.0\ \Omega$

Typical circuits

3D Printer Heated Bed / High-Current Heater Controller (12V/24V)

At $10\text{ A}$ current draw (typical 12V 120W heated bed), power dissipation is only $P = I^2 \times R = 10^2 \times 0.0131 = 1.31\text{ W}$ , allowing the MOSFET to run cool:

text

        +12V / +24V Heated Bed Supply
           │
         [ HEATED BED (120W - 250W) ]
           │
        [Pin 2: DRAIN]
         IRLB8721
        [Pin 3: SOURCE] ─── GND (Common System Ground)
           │
        [Pin 1: GATE] ◄───[ R_gate = 100Ω ]───◄ MCU Heated Bed PWM Pin
           │
        [ R_pulldown = 100kΩ ]
           │
          GND

Selection & substitutes

Part Number	$V_{DSS}$	$I_D$	$R_{DS(on)}$ at 4.5V	Key Advantage
IRLB8721	$30\text{ V}$	$62\text{ A}$	$13.1\text{ m}\Omega$	Ultra-low gate charge ( $8.4\text{ nC}$ ), fast switching
IRLB8743	$30\text{ V}$	$150\text{ A}$	$4.2\text{ m}\Omega$	Even lower $R_{DS(on)}$ for extreme current loads ( $> 20\text{A}$ )
IRLZ44N	$55\text{ V}$	$47\text{ A}$	$25\text{ m}\Omega$	Higher voltage rating ( $55\text{V}$ )

Common mistakes

Exceeding $30\text{V}$ maximum drain-source voltage: Unlike $55\text{V}$ or $100\text{V}$ MOSFETs, the IRLB8721 has an absolute maximum $V_{DSS}$ of $30\text{V}$ . Do not use it on $36\text{V}$ or $48\text{V}$ power systems (use the IRL540N instead).
Missing gate pull-down resistor: Always install a $10\text{ k}\Omega \dots 100\text{ k}\Omega$ resistor between Gate and Source to hold the MOSFET in the OFF state while the microcontroller is powering up or flashing firmware.

Notes

Suffix Identification: The standard lead-free through-hole model is IRLB8721PBF.

Interface	3.3V, 4.5V, and 10V Gate Drive Compatible
Package	TO-220AB