How to Use IRLB8721 MOSFET: Examples, Pinouts, and Specs

The IRLB8721 is an N-channel MOSFET designed for high-speed switching applications. It features low on-resistance and high current handling capabilities, making it ideal for power management, motor control, and other high-power electronic circuits. Its robust design and efficiency make it a popular choice for hobbyists and professionals alike.

• Motor drivers for DC and stepper motors
• Power management in battery-operated devices
• Switching regulators and converters
• LED dimming and control circuits
• General-purpose high-current switching

The IRLB8721 is a high-performance MOSFET with the following key specifications:

The IRLB8721 comes in a TO-220 package with three pins. The pinout is as follows:

1. Gate Control: Connect the Gate pin to a control signal (e.g., from a microcontroller or logic circuit). Ensure the gate voltage (V_GS) is within the specified range (typically 5V to 10V for full switching).
2. Drain-Source Path: Connect the load (e.g., motor, LED, or other device) between the Drain pin and the positive supply voltage. The Source pin should be connected to ground.
3. Gate Resistor: Use a resistor (typically 10Ω to 100Ω) between the control signal and the Gate pin to limit inrush current and prevent oscillations.
4. Flyback Diode: For inductive loads (e.g., motors or relays), add a flyback diode across the load to protect the MOSFET from voltage spikes during switching.

Below is an example of how to use the IRLB8721 to control a DC motor with an Arduino UNO:

• Gate (G): Connect to Arduino digital pin (e.g., D9) through a 100Ω resistor.
• Drain (D): Connect to one terminal of the motor.
• Source (S): Connect to ground.
• Motor: Connect the other terminal to the positive supply voltage.
• Flyback Diode: Place a diode (e.g., 1N4007) across the motor terminals, with the cathode connected to the positive supply.

// Example code to control a DC motor using the IRLB8721 MOSFET
// Connect the Gate pin of the MOSFET to Arduino pin 9

const int motorPin = 9; // Pin connected to the MOSFET Gate

void setup() {
  pinMode(motorPin, OUTPUT); // Set the motor pin as an output
}

void loop() {
  // Turn the motor ON
  digitalWrite(motorPin, HIGH); // Apply HIGH signal to the Gate
  delay(2000); // Keep the motor running for 2 seconds

  // Turn the motor OFF
  digitalWrite(motorPin, LOW); // Apply LOW signal to the Gate
  delay(2000); // Keep the motor off for 2 seconds
}

• Ensure the Gate voltage (V_GS) is sufficient to fully turn on the MOSFET. For logic-level operation, a V_GS of 5V is typically adequate.
• Avoid exceeding the maximum voltage and current ratings to prevent damage.
• Use proper heat dissipation methods (e.g., a heatsink) if operating at high currents.

1. MOSFET Overheating

   • Cause: Insufficient heat dissipation or operating beyond current limits.
   • Solution: Use a heatsink and ensure the current is within the specified range.

2. MOSFET Not Switching

   • Cause: Insufficient Gate voltage or incorrect wiring.
   • Solution: Verify the Gate voltage is at least 5V and check the circuit connections.

3. Load Not Operating

   • Cause: Incorrect load connection or damaged MOSFET.
   • Solution: Check the load connections and test the MOSFET with a multimeter.

Q: Can the IRLB8721 be used with a 3.3V logic signal?
A: While the IRLB8721 is not guaranteed to fully switch on at 3.3V, it may work for low-current applications. For reliable operation, use a logic-level MOSFET or a Gate driver circuit.

Q: Do I need a heatsink for the IRLB8721?
A: A heatsink is recommended if the MOSFET is handling high currents or operating for extended periods.

Q: Can I use the IRLB8721 for AC loads?
A: No, the IRLB8721 is designed for DC applications. For AC loads, consider using a TRIAC or other suitable component.