The Problem: Exceeding the Safe Operating Area (SOA)

When working with MOSFETs, many hobbyists overlook one crucial spec: the Safe Operating Area (SOA). Exceeding it can quickly destroy your device. The SOA defines the limits of voltage, current, and power a MOSFET can handle at the same time. Ignoring this often results in overheating, thermal runaway, or even permanent failure.

The Solution: Read and Respect the SOA Graph :

Always check the datasheet’s SOA chart before finalizing your circuit. If you’re switching inductive loads or working in linear mode (e.g., analog dimming), ensure your MOSFET stays within safe limits under worst-case conditions.

Practical Example :

Let’s say you’re controlling a 12V motor drawing 4A using a MOSFET. If the drain-source voltage momentarily spikes to 10V during switching, the instantaneous power = 10V × 4A = 40W. If your MOSFET’s SOA curve limits power dissipation to 30W in that region, you’re pushing it beyond its limit—risking failure!

Sample Calculation :

For safe operation:

P = V × I = 8V × 4A = 32W

Choose a MOSFET rated for >40W dissipation in the required SOA zone, or parallel two MOSFETs to share the load.

Product Suggestion :

Pick quality Made in India MOSFETs with detailed SOA charts and reliable thermal handling.

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