Power conversionBench electronicsSpecialist reuse

Power MOSFET

Also called HEXFET, logic level FET, VRM FET.

Worth pulling only when the part number is readable and you look it up. Motherboard FETs are often marked with a short code, not the full part number, and the code is a rabbit hole.

If you are new to this category

These parts change wall power into the lower voltage a device uses. A sealed supply with a label is the safer kind. An open board from a lamp can still be connected to the wall on the side that looks like low voltage. Isolated means the output is not electrically connected to the wall. If you are not sure, treat the output as live.

Read the label out loud: volts, amps, and the polarity symbol. Then measure. A number you remember from a similar brick is not a measurement.

A sealed supply versus an open board

Left: a brick. The label is your spec, and the plastic is the safety barrier. Right: a board taken out of a lamp or a charger. Unless you have checked that the output is isolated from the prongs, do not let it touch a project you will handle while it is plugged in.

Stored high voltage. Capacitors hold a charge with the cord in your other hand. Microwave HV capacitors, CRT anodes, xenon flash caps, and primary bulk caps are the usual ones.
Mains voltage. Line voltage, and the DC bus just after the rectifier, both kill. A disconnected cord is not a discharged supply.

Specification. The right-hand column is what is typical. The label on the part in your hand wins if they disagree.
What to look for	Usual figure
What you need	Vds, Rds(on), Vgs(th), Id, package. A logic-level FET fully enhances at 4.5 V or below. A standard FET at 10 V.
Body diode	Present. The diode test will show it. That does not identify the FET.

Volts are electrical pressure, amps are how much current is flowing, and ohms are how hard the part resists that flow. A higher voltage than the part was built for is how salvage parts die on the bench. If a cell in the table says “read the stamp”, that stamp is the whole specification.

What people actually use it for

A known part you have a datasheet for
Low-side switching of a DC load

Leave this one when

The marking is a house code you cannot resolve. Anonymous FETs are how prototypes die at the worst moment.

Buying a new one is the better idea when

Almost always, unless this exact part number is one you already use.

How to tell if this one still works

Diode test of the body diode to confirm it is not shorted in all directions. A shorted FET reads near 0 both ways between drain and source.

Tools you will want: Meter, Datasheet.

Where people actually find it

1 notes, most useful first. “Leave it” means the part is in that machine and you should not take it: it is dangerous, worn out, or only useful if you already know that exact repair.

Harvest at a glance
From	Call	How many	How often	Where it sits
Desktop PC	Leave it	several	usually	VRM.

Leave it — present, not yours to reuseDesktop PCseveral · usually
In this particular machine
Short house markings, not a catalog number you can trust at a glance.
Where to look
VRM.
How to get it out
Leave them unless the full part number is printed and you use that part.
The condition to expect
Unknown.