P-MOSFET

A P-MOSFET switches the positive side of a circuit. With S connected to the positive supply, a gate voltage sufficiently below S lets current flow from S to D. Bringing G back to S turns it off.

A resistor between G and S helps keep it off. Check the pinout: a P-MOSFET is not a direct replacement for an N-MOSFET.

SparkVille’s little tram dims its glowing route map for evening trips. A P-MOSFET switches the lights’ positive supply.