When using MOSFETs in your circuit—especially in switching applications like SMPS or motor drivers—switching transients can cause unexpected spikes, ringing, or even damage. Understanding and managing these fast voltage/current changes is key to a reliable design.

🔧 The Problem: Voltage Spikes During Switching

During fast switching, especially in inductive loads, the drain voltage can spike due to parasitic inductance and rapid current changes (di/dt). This can exceed the MOSFET’s rated voltage, leading to failure or erratic behavior.

✅ The Solution : Snubber Circuit + Gate Resistor

You can tame transients using a RC snubber across the MOSFET or a flyback diode for inductive loads. A small-value gate resistor (e.g., 10–100Ω) slows down the switching slightly and helps suppress ringing.

🔍 Practical Example: Controlling a DC Motor

Imagine switching a 12V DC motor using an IRF540N MOSFET. On switching off, a 40V spike appears across the drain. Adding a 100Ω + 100nF snubber across drain-source and a 22Ω gate resistor smooths the waveform and keeps the MOSFET safe.

🧮 Sample Calculation: Snubber Resistor

Choose R ≈ √(L/C) for critically damped response.
If L ≈ 10µH, C = 100nF → R ≈ √(10e-6 / 100e-9) ≈ 10Ω

🛒 Product Suggestion: Made in India Components

• ⚙️ Shop MOSFETs

• 🔧 [Shop resistors]

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