Power Electronics
While a BJT is driven by current, a MOSFET is driven by voltage: once the gate (G) voltage exceeds the threshold (Vth), the channel between D and S opens. The gate behaves like a capacitor — it draws no current at DC; driving it is therefore effortless and fast.
PWM is the most efficient way to throttle power: you open and close the switch thousands of times per second and change only the fraction of time it stays on (duty). 70% duty → the load "feels" 70% of the voltage on average. Dimmers, motor drives and heaters all work on this principle — because the switch is either fully on or fully off, it never heats up in between.
Still, it is not free: conduction costs I²·RDS(on), and every turn-on/turn-off adds a small switching loss (which grows with frequency). The Power Analysis tab shows these losses live — this is where the engineering trade-off is negotiated.
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