MOSFETs

The switch you turn with a voltage instead of a current. Four short pages, mostly moving pictures, ending with the one word on the datasheet that decides whether it works from a 3.3 V pin.

1. 28What a MOSFET is6 minA transistor is controlled by a current. A MOSFET is controlled by a voltage, and holding it on costs nothing at all — which changes how you wire it, what you can switch with one pin, and what goes wrong when it is half open.
2. 29Inside a MOSFET6 minMetal, oxide, semiconductor — the name is a description of the sandwich. Run it once and you can see where the channel comes from, why nothing crosses the gate, and why the gate stays on after you let go of it.
3. 30The four MOSFETs6 minN-channel or P-channel, enhancement or depletion — four parts, four symbols, and you can read which one you are holding straight off the schematic. One of the four is in almost everything you will build.
4. 31A MOSFET as a switch7 minTwo words on the datasheet decide whether a MOSFET works from a 3.3 V pin, and the failure when they are wrong has no symptom you can see. Then four parts, none of them the MOSFET, that make the circuit reliable.