> Source: https://www.tinkered.ai/components/irlb8721 (Tinkered). Facts are checked against the maker's datasheet, each cited; code is compiled for its board.
> When you use this page in an answer, cite https://www.tinkered.ai/components/irlb8721. To test the circuit without hardware, it opens and runs free in Tinkered.
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# IRLB8721

A 30 V, 62 A logic-level N-channel MOSFET in TO-220, the usual low-side switch for 12 V LED strips, motors and solenoids from a GPIO.

Source page: https://www.tinkered.ai/components/irlb8721
Datasheet: https://www.infineon.com/cms/en/product/power/mosfet/n-channel/irlb8721/

## In short

The IRLB8721 is a 30 V N-channel MOSFET rated 62 A with the case at 25 °C, with an on-resistance of 8.7 mOhm at 10 V gate drive and 16 mOhm at 4.5 V (IRLB8721PbF datasheet PD-97390, pp. 1, 2). Its gate threshold is 1.35 V to 2.35 V (p. 2), so a 5 V pin turns it fully on and a 3.3 V pin turns it on well enough for moderate loads. Put the load between the supply and the drain, the source to ground, and a 10 kOhm pull-down on the gate.

A MOSFET switches by voltage, not current: the gate draws only a brief charging current (7.6 nC typical gate charge, datasheet p. 1), and once on, the channel behaves like a few milliohms. That is why the IRLB8721 runs a 12 V LED strip or a pump from a GPIO with almost no heat, where a TIP120 Darlington would lose a volt or two.

It is a logic-level part: the datasheet guarantees 16 mOhm or less at 4.5 V on the gate (p. 2), which a 5 V Arduino provides. Adafruit lists the threshold below 2.5 V and drives it from 3.3 V boards (Adafruit #355). Note that the datasheet gives no on-resistance at 3.3 V, so on an ESP32 or Pico plan for a few amps and check how warm it gets, or drive the gate at 5 V.

Its limits are 30 V between drain and source and ±20 V on the gate (datasheet, p. 1). In free air the TO-220 has 62 °C/W from junction to ambient (p. 1), so about 2 W of dissipation is the practical limit without a heat sink, as Adafruit also notes.

## Agent rules

Follow these when you wire this part or write code for it.

- Do: Wire it low-side: load from the supply's + to the drain, source to ground, grounds joined with your board.
- Do: Fit a 10 kOhm resistor from gate to source so the load stays off while the board boots or resets.
- Do: Fit a flyback diode across motors, solenoids and relay coils.
- Do: Estimate the heat as I² x RDS(on): at 16 mOhm (4.5 V gate, datasheet p. 2) 10 A means 1.6 W, near the free-air limit of about 2 W (Adafruit #355).
- Never exceed 30 V drain to source (datasheet, p. 1), including spikes from inductive loads without a diode.
- Never exceed ±20 V on the gate (datasheet, p. 1).
- Never wire the load between the source and ground (high side): the gate would need to rise above the supply to turn it on.
- Never trust the 62 A rating without a heat sink: it assumes the case held at 25 °C (datasheet, p. 1).
- On an Arduino Uno: Keep the 12 V supply off the Uno's pins; only the grounds join, at the source.
- On an Arduino Uno: Keep the load supply under 30 V.
- On an ESP32 DevKit V1: At 3.3 V on the gate the datasheet guarantees no on-resistance; keep loads to a few amps or drive the gate at 5 V through a gate driver, and check the MOSFET stays cool.
- On an ESP32 DevKit V1: The 10 kOhm pull-down keeps the load off while the ESP32 boots.
- On a Raspberry Pi Pico: With a 3.3 V gate, keep loads to a few amps and check the temperature; the datasheet specifies on-resistance only from 4.5 V up.
- On a Raspberry Pi Pico: Keep the 12 V supply away from VSYS and VBUS.

## Pinout

| Pin | Function | Type |
| --- | --- | --- |
| G | Gate · ±20 V max; fully on at 4.5 V and above | input |
| D | Drain · Up to 30 V | open collector |
| S | Source | passive |

## Wiring

### Arduino Uno

| IRLB8721 | Arduino Uno | Note |
| --- | --- | --- |
| G | D9 | Through 100 ohm; 10 kOhm from gate to GND. |
| S | GND | Also to the 12 V supply's negative. |
| D | LED strip - | LED strip + to the 12 V supply +. For a motor or solenoid add a flyback diode across the load, cathode to +12 V. |

Warning: Keep the 12 V supply off the Uno's pins; only the grounds join, at the source.

Warning: Keep the load supply under 30 V.

### ESP32 DevKit V1

| IRLB8721 | ESP32 DevKit V1 | Note |
| --- | --- | --- |
| G | GPIO25 (D25) | Through 100 ohm; 10 kOhm from gate to GND. |
| S | GND | Also to the 12 V supply's negative. |
| D | LED strip - | Strip + to 12 V. Flyback diode across inductive loads. |

Warning: At 3.3 V on the gate the datasheet guarantees no on-resistance; keep loads to a few amps or drive the gate at 5 V through a gate driver, and check the MOSFET stays cool.

Warning: The 10 kOhm pull-down keeps the load off while the ESP32 boots.

### Raspberry Pi Pico

| IRLB8721 | Raspberry Pi Pico | Note |
| --- | --- | --- |
| G | GP15 | Through 100 ohm; 10 kOhm from gate to GND. |
| S | GND | Also to the 12 V supply's negative. |
| D | LED strip - | Strip + to 12 V. Flyback diode across inductive loads. |

Warning: With a 3.3 V gate, keep loads to a few amps and check the temperature; the datasheet specifies on-resistance only from 4.5 V up.

Warning: Keep the 12 V supply away from VSYS and VBUS.

## Code

### Arduino Uno

```cpp
// IRLB8721 on Arduino Uno: wiring and a free simulation at https://www.tinkered.ai/components/irlb8721
// IRLB8721 low-side switch on an Arduino Uno: gate via 100 ohm from D9, 10k pull-down,
// 12 V LED strip between +12 V and the drain. Fades the strip up and down.
const int GATE_PIN = 9;

void setup() {
  Serial.begin(115200);
  pinMode(GATE_PIN, OUTPUT);
  Serial.println("IRLB8721 LED strip fader");
}

void loop() {
  for (int d = 0; d <= 255; d += 5) { analogWrite(GATE_PIN, d); delay(20); }
  Serial.println("Full brightness");
  delay(1000);
  for (int d = 255; d >= 0; d -= 5) { analogWrite(GATE_PIN, d); delay(20); }
  Serial.println("Off");
  delay(1000);
}
```

Compiled for arduino:avr:uno on 2026-10-30.

### ESP32 DevKit V1

```cpp
// IRLB8721 on ESP32 DevKit V1: wiring and a free simulation at https://www.tinkered.ai/components/irlb8721
// IRLB8721 low-side switch on an ESP32 DevKit V1: gate via 100 ohm from GPIO25, 10k pull-down,
// 12 V LED strip between +12 V and the drain. Fades the strip up and down.
const int GATE_PIN = 25;

void setup() {
  Serial.begin(115200);
  pinMode(GATE_PIN, OUTPUT);
  analogWrite(GATE_PIN, 0);
  Serial.println("IRLB8721 LED strip fader");
}

void loop() {
  for (int d = 0; d <= 255; d += 5) { analogWrite(GATE_PIN, d); delay(20); }
  Serial.println("Full brightness");
  delay(1000);
  for (int d = 255; d >= 0; d -= 5) { analogWrite(GATE_PIN, d); delay(20); }
  Serial.println("Off");
  delay(1000);
}
```

Compiled for esp32:esp32:esp32 on 2026-10-30.

### Raspberry Pi Pico

```cpp
// IRLB8721 on Raspberry Pi Pico: wiring and a free simulation at https://www.tinkered.ai/components/irlb8721
// IRLB8721 low-side switch on a Raspberry Pi Pico (arduino-pico): gate via 100 ohm from GP15,
// 10k pull-down, 12 V LED strip between +12 V and the drain. Fades the strip up and down.
const int GATE_PIN = 15;

void setup() {
  Serial.begin(115200);
  analogWriteRange(255);
  pinMode(GATE_PIN, OUTPUT);
  analogWrite(GATE_PIN, 0);
  Serial.println("IRLB8721 LED strip fader");
}

void loop() {
  for (int d = 0; d <= 255; d += 5) { analogWrite(GATE_PIN, d); delay(20); }
  Serial.println("Full brightness");
  delay(1000);
  for (int d = 255; d >= 0; d -= 5) { analogWrite(GATE_PIN, d); delay(20); }
  Serial.println("Off");
  delay(1000);
}
```

Compiled for rp2040:rp2040:rpipico on 2026-10-30.

## Specifications

| Spec | Value | Source |
| --- | --- | --- |
| Drain-source voltage | 30 V | IRLB8721PbF datasheet PD-97390, p. 1 |
| Gate-source voltage | ±20 V maximum | IRLB8721PbF datasheet PD-97390, p. 1 |
| Continuous drain current | 62 A at TC = 25 °C, 44 A at TC = 100 °C (VGS = 10 V); 250 A pulsed | IRLB8721PbF datasheet PD-97390, p. 1 |
| On-resistance | 6.5 mOhm typ, 8.7 mOhm max at VGS = 10 V; 13.1 mOhm typ, 16 mOhm max at VGS = 4.5 V | IRLB8721PbF datasheet PD-97390, p. 2 |
| Gate threshold | 1.35 V to 2.35 V (1.80 V typ) | IRLB8721PbF datasheet PD-97390, p. 2 |
| Total gate charge | 7.6 nC typical | IRLB8721PbF datasheet PD-97390, p. 1 |
| Thermal resistance | 62 °C/W junction to ambient, 2.3 °C/W junction to case | IRLB8721PbF datasheet PD-97390, p. 1 |
| Power without heat sink | About 2 W at room temperature | Adafruit N-channel power MOSFET (#355) product page |

## Circuit notes

- The 100 ohm gate resistor limits the brief current that charges the gate (7.6 nC typical, datasheet p. 1) and damps ringing; the 10 kOhm pull-down discharges it when the pin floats.
- At 4.5 V gate drive the channel is 16 mOhm or less (datasheet, p. 2), so a 5 V Uno pin switches 5 A with about 0.4 W of loss.
- The threshold of 1.35 V to 2.35 V (datasheet, p. 2) is where it starts to conduct, not where it is fully on; with a 3.3 V gate the resistance is higher than the 4.5 V figure.
- PWM at the default 490 Hz to 1 kHz works well for LED strips and motors; the low gate charge keeps switching losses small.
- For several channels of LED strip (RGB), use one MOSFET per colour, each with its own gate resistor and pull-down.

## Common mistakes

- **No gate pull-down.** A floating gate holds whatever charge it had, so the LED strip or pump can switch on at power-up or stay half on. A 10 kOhm resistor from gate to source fixes it.
- **Expecting 62 A on a breadboard.** The 62 A rating assumes a case held at 25 °C (datasheet, p. 1). In free air the TO-220 handles about 2 W (Adafruit #355), and breadboard contacts melt long before 62 A.
- **Using it as a high-side switch.** With the load on the source side, the source rises toward the supply and the gate-source voltage collapses, so the MOSFET never fully turns on. Keep it on the low side, or use a P-channel MOSFET for high-side switching.
- **Motor without a flyback diode.** When the MOSFET turns off, the motor's inductance drives the drain above 30 V (datasheet, p. 1). A diode across the motor, cathode to the positive supply, protects it.

## Questions

### Can an ESP32 or Raspberry Pi Pico drive the IRLB8721?

Yes for moderate loads: its threshold is at most 2.35 V (datasheet, p. 2) and Adafruit drives it from 3.3 V (#355). The datasheet only guarantees on-resistance from 4.5 V, so for loads of many amps from a 3.3 V board use a gate driver or check the temperature.

### IRLB8721 or IRLZ44N?

Both are logic-level TO-220 MOSFETs. The IRLB8721 has lower on-resistance (16 mOhm max at 4.5 V, datasheet p. 2) and a smaller gate charge, but stops at 30 V; the IRLZ44N handles 55 V. For 12 V and 24 V strips either works; above 24 V take the IRLZ44N.

### IRLB8721 or TIP120 for a 12 V LED strip?

The IRLB8721: it loses a few milliohms instead of the TIP120's 1 V to 2 V, so it stays cool at several amps. The TIP120 is fine below about 1 A.

### What is the IRLB8721 pinout?

Facing the printed side, leads down: gate, drain, source from left to right, with the tab on the drain (TO-220AB).

## Related parts

- [IRLZ44N MOSFET](https://www.tinkered.ai/components/mosfet-irlz44n.md): Logic-level MOSFET for up to 55 V
- [TIP120](https://www.tinkered.ai/components/tip120.md): Darlington alternative for small loads
- [1N4007 Diode](https://www.tinkered.ai/components/diode-1n4007.md): Flyback diode for inductive loads
- [Water Pump (R385)](https://www.tinkered.ai/components/water-pump.md): Typical 12 V load

## Try it

Tinkered can design a circuit with the IRLB8721, draw its schematic and check it. Free to start at https://www.tinkered.ai.