How it works
An N-Channel MOSFET is a voltage-controlled semiconductor switch, making it fundamentally different from current-controlled bipolar transistors (like the NPN). To turn a MOSFET on, you simply apply a voltage to its Gate relative to its Source.
Because the Gate is electrically isolated from the rest of the transistor by a microscopic layer of glass (silicon dioxide), it draws virtually zero continuous current. This makes MOSFETs incredibly easy to drive directly from microcontrollers. Once turned fully on, the path between Drain and Source acts like a very low-value resistor (Rds_on), allowing them to switch massive currents (often 10A to 50A) with minimal heat.
They are the backbone of modern power electronics, dominating motor drivers, 3D printer heated beds, and high-speed switching power supplies.