MOSFET Gate Driver Design

Driving a power MOSFET gate correctly is non-trivial. The gate is a capacitor (10-100nF for a power FET) that must be charged and discharged quickly for fast switching.

A simple gate resistor (10-47 ohm) from the microcontroller GPIO limits the drive current to protect the GPIO but slows gate transitions significantly. For a switching supply or motor driver, slow transitions mean more switching loss and heat.

A dedicated gate driver IC (TC4420, UCC27517) provides 4-9A peak gate drive from a logic-level input. This switches a 10nF gate in under 10ns instead of 500ns with a 47-ohm GPIO drive. The difference in switching loss at 100kHz is dramatic: 100mW vs 5mW for the same FET and conditions. For any circuit switching above a few kHz, gate driver ICs are essential.