3.3 MOSFETs

Outcome 3 of 9 in domain 3 · Semiconductors and analog

Switching, gate drive, Rds(on), losses, dissipation.

My targets

I declare:

Explain gate, drain, source, the threshold voltage Vgs, and read Rds(on) on the datasheet at the Vgs actually available.
Choose a logic-level MOSFET to switch a 12 V or 48 V load from a microcontroller, and justify it.
Calculate conduction losses (I² × Rds(on)) and estimate the heating without a heatsink.
Explain why the gate draws current at every switching and what a gate driver brings in fast PWM.
Build a MOSFET PWM switch, observe Vgs and Vds on the oscilloscope and spot the switching time.
Distinguish N and P MOSFETs, low-side and high-side switching, and explain the intrinsic (body) diode and what it does in a bridge.
Diagnosis: a MOSFET that dies shorted on a motor controller, overvoltage, overheating or floating gate; how to know.