Which MOSFETs or BJTs Can Be Used with Raspberry Pi GPIO?
Controlling external devices such as motors, LED strips, solenoids, or relays with a Raspberry Pi is one of the most common beginner and intermediate electronics projects. However, many makers face problems when they connect their Pi’s 3.3V GPIO pins directly to a transistor or MOSFET that is not designed for low-voltage logic levels.
In this article, we’ll explore which MOSFETs and BJTs work best with Raspberry Pi GPIO pins, what makes a transistor compatible, and how to choose the right one for your projects. We’ll also compare popular options such as the IRF520N and IRLZ44N, and list recommended alternatives.
Why Do We Need Transistors or MOSFETs with Raspberry Pi?
The Raspberry Pi’s GPIO pins:
- Operate at 3.3V logic levels
- Provide a maximum current of only ~16 mA per pin (with a total budget of around 50 mA across all GPIOs)
This is not enough to power motors, relays, or even high-power LEDs directly. That’s where MOSFETs and BJTs come in — they act as electronic switches or amplifiers that let the small signal from the Pi control larger voltages and currents.
MOSFET vs BJT: Which One Should You Use?
Both MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) and BJTs (Bipolar Junction Transistors) can be used with the Raspberry Pi, but they have different characteristics.
MOSFET Advantages
- High efficiency (very low power loss when fully on)
- Suitable for switching large currents
- Logic-level MOSFETs can turn fully on with just 3.3V from the Pi
BJT Advantages
- Easy to understand for beginners
- Widely available in small packages
- Good for small loads (relays, LEDs, buzzers)
Quick Comparison Table
| Feature | MOSFETs (Logic Level) | BJTs |
|---|---|---|
| Control Voltage | Works well at 3.3V (if logic-level) | Needs base current, usually fine at 3.3V |
| Current Handling | Very high (10A–50A possible) | Usually lower (few hundred mA to 1–2A) |
| Switching Speed | Very fast | Moderate |
| Efficiency | Very high | Lower (voltage drop across BJT) |
| Complexity | Slightly higher | Simpler for beginners |
If you want to drive high-power devices, choose a logic-level MOSFET.
For simple low-power switching, a BJT is often enough.
Why the IRF520N Does Not Work with Raspberry Pi
Many beginners buy cheap “IRF520 MOSFET driver modules” online, expecting them to work with Raspberry Pi. Unfortunately, the IRF520N is a standard MOSFET, not a logic-level MOSFET.
- It requires around 10V at the gate to turn on fully.
- At 3.3V from Raspberry Pi, it only turns partially on.
- This leads to overheating, low current output, and sometimes a non-working circuit.
So while the IRF520N might work on an Arduino (5V logic) for small loads, it is not reliable for Raspberry Pi projects.
Recommended MOSFETs for Raspberry Pi
When choosing MOSFETs, look for logic-level MOSFETs with:
- Vgs(th) < 2V (Gate threshold voltage)
- Low Rds(on) at 3.3V (for less heat and higher efficiency)
Popular Choices
| MOSFET Model | Package | Max Current | Works at 3.3V GPIO? | Notes |
|---|---|---|---|---|
| IRLZ44N | TO-220 | 47A | ✅ Yes | Excellent for motors and LED strips |
| IRL540N | TO-220 | 28A | ✅ Yes | Good general-purpose logic MOSFET |
| AO3400/AO3402 | SMD | 5–6A | ✅ Yes | Great for compact PCB projects |
| STP55NF06L | TO-220 | 50A | ✅ Yes | Strong performer, widely used |
| IRF520N | TO-220 | 9.2A | ❌ No | Needs 10V at gate, avoid with Pi |
👉 If you’re using a breadboard setup with wires and external loads, the IRLZ44N is one of the best choices. It can directly replace the IRF520N in most circuits and will switch cleanly with 3.3V logic.
Recommended BJTs for Raspberry Pi
If your load is smaller (like controlling a relay, LED, or buzzer), a BJT transistor can be a simple and effective choice.
Popular Choices
| BJT Model | Type | Max Current | Typical Use with Raspberry Pi |
|---|---|---|---|
| 2N2222 | NPN | 600mA | Driving relays, small motors, LEDs |
| BC547 | NPN | 100mA | General small signal switching |
| TIP120 | NPN Darlington | 5A | Higher current loads, simple circuits |
| 2N3904 | NPN | 200mA | LED strips, buzzers, sensors |
With BJTs, don’t forget to add a base resistor (usually 1kΩ–10kΩ) to protect the Raspberry Pi GPIO pin.
Wiring Example: Using IRLZ44N with Raspberry Pi
Here’s a simple wiring setup for controlling a 12V LED strip using an IRLZ44N:
- Gate (pin 1) → Raspberry Pi GPIO (through 220Ω resistor)
- Drain (pin 2, metal tab) → Negative end of the LED strip
- Source (pin 3) → Ground (shared with Raspberry Pi GND)
- Positive of LED strip → +12V power supply
Don’t forget: Always connect the grounds together (Raspberry Pi GND and external power GND).
Key Tips for Choosing Transistors for Raspberry Pi
- Always pick logic-level MOSFETs for 3.3V GPIO control
- Use BJTs for low-power loads like relays, LEDs, or buzzers
- Check the datasheet for Vgs(th) (MOSFET) or hFE (BJT gain)
- Ensure the transistor can handle both current and voltage of your load
- Add a flyback diode (e.g., 1N4007) when switching inductive loads (motors, relays, solenoids)
Conclusion
Not every transistor is suitable for the Raspberry Pi’s 3.3V GPIO pins. While modules like the IRF520N may seem attractive, they are not reliable at 3.3V logic. Instead, you should choose logic-level MOSFETs such as the IRLZ44N, IRL540N, or AO3400, or use classic BJTs like 2N2222 and BC547 for smaller tasks.
By picking the right transistor, you can safely and efficiently control high-power devices from your Raspberry Pi without risking damage or frustration.
With the right choice, your Raspberry Pi can power everything from LED strips and fans to robot motors and home automation relays — opening up endless possibilities for your projects.
