🔧 The Problem :

MOSFETs are powerful and efficient switches, but when used with inductive loads (motors, solenoids, relays), they’re vulnerable to avalanche breakdown. This occurs when a sudden voltage spike—caused by inductive energy—exceeds the MOSFET’s drain-source breakdown voltage (V_DSS), damaging the part.

✅ The Solution :

Use a freewheeling diode (also called a flyback diode) across inductive loads. Alternatively, for high-speed switching, you can add a TVS diode across the MOSFET or select a MOSFET rated for avalanche energy. This protects your design from sudden spikes.

🔍 Real-World Example :

An engineer in Pune powering a small 12V DC fan via MOSFET noticed random failures. After switching to an avalanche-rated MOSFET and placing a 1N5822 diode across the fan, the issue was resolved and no further failures occurred.

✏️ Sample Calculation :

Let’s say:

• Inductance = 100µH

• Peak current = 2A

• Inductive energy = ½ × L × I² = 0.5 × 100×10⁻⁶ × 4 = 0.2mJ

Ensure your MOSFET’s avalanche energy rating (E_AS) exceeds this value.

🛒 Product Suggestion – Made in India

• Try avalanche-rated MOSFETs ➜
  
  

• Or use a TVS diode ➜
  
  

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