POV: You Are a Charge in a MOSFET Gate

Lesson notes

Key points

• The gate driver pushes you out, and you pile onto the gate, which behaves like a small capacitor.
• As more of you arrive, gate-source voltage rises past the threshold and a conducting channel forms below you.
• Now drain voltage collapses, and you get stuck feeding the Miller capacitance, so VGS sits flat on a plateau.
• Guess why drivers deliver amps: the faster you arrive, the shorter the switching transition and the lower the switching loss.

Definitions

Miller plateau

Flat VGS period while gate charge feeds gate-drain capacitance as drain voltage falls

Takeaway: A MOSFET gate is a capacitor; drive it hard to switch fast.

Gate capacitanceThreshold voltageMiller plateauFast switching