How to Qualitatively Test MOSFETs with a Multimeter

Step 1: Identify MOSFET Type

MOSFETs come in N-channel and P-channel types. Use your multimeter’s diode test mode to determine the type:

• N-channel: Connect the red probe to the source (S) and the black probe to the drain (D). A reading of 0.4–0.9V indicates a healthy parasitic diode . Reverse the probes (red to D, black to S) for an open circuit (OL) reading .

• P-channel: Reverse the probe connections. A 0.4–0.9V reading on the first test confirms a P-channel MOSFET .

Step 2: Check for Shorts or Opens

Switch to resistance mode (Ω) and test all pin combinations:

• G-S and G-D: Readings should be high resistance (MΩ). Low values indicate a damaged gate .

• D-S: Measure resistance with the gate floating. A healthy MOSFET shows high resistance. If shorted (0Ω) or open (OL), replace the device .

Step 3: Test Gate Control

Charge the gate by briefly connecting the red probe to G and the black probe to S (N-channel) or D (P-channel). Recheck D-S resistance—it should drop significantly, confirming proper channel activation .

Safety & Best Practices

• Discharge the MOSFET by shorting all pins before testing to avoid false readings .

• Avoid static electricity: Use anti-static tools and ground yourself when handling MOSFETs .

• Refer to datasheets: For specific voltage thresholds and pin configurations .

Why Choose YFW Microelectronics?

At YFW Microelectronics, we design high-reliability MOSFETs with built-in protection features to simplify testing. Our products undergo rigorous quality control, ensuring stable performance in power management, motor control, and more. Visit yfwdiode.com to explore our range.

By following these steps, you can efficiently diagnose MOSFET issues and maintain the integrity of your circuits. Always prioritize safety and precision in your testing procedures.