A breakdown of the four basic MOSFET switching topologies for controlling a two-wire load: high-side N-channel, high-side P-channel, low-side N-channel, and low-side P-channel. The low-side N-channel is the simplest and cheapest option since its gate drive is referenced to circuit ground. High-side switches are required when one load terminal must be tied to ground for safety or EMI reasons. P-channel devices offer simpler gate drive than N-channel in high-side configurations but have worse performance and fewer choices. High-side N-channel requires bootstrap or isolated gate drive circuitry. Low-side P-channel is essentially never used. The post also emphasizes adding a freewheeling diode in parallel with inductive loads to prevent MOSFET breakdown.
