MOSFET Switching Ripple Reduction: Easy Fix for Smooth Operation
The Problem :
MOSFETs are widely used in switching circuits, but they often introduce voltage ripple or noise due to rapid switching. This ripple can affect sensitive components and reduce overall circuit efficiency. Ripple occurs when the MOSFET switches too fast, causing unwanted high-frequency oscillations.
The Solution :
A practical fix to reduce switching ripple is by adding a small gate resistor (typically 10–100 ohms) between the MOSFET driver and the gate pin. This resistor slows down the switching speed, reducing high-frequency noise and improving stability.
Practical Example :
Switching a DC Motor
Consider controlling a DC motor using an IRF540N MOSFET. Without a gate resistor, the motor experiences noise and unpredictable behavior. Adding a 47-ohm resistor smooths the switching, preventing ripple and ensuring steady motor performance.
Sample Calculation :
To size the resistor:
Gate capacitance of IRF540N ≈ 1700 pF
Target switching time = 200 ns
Using the formula:
R=CgsT=1700×10−12200×10−9≈47 ohms.
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