Asked by: Dulcerina Klockenkampertechnology and computing digital audio
Can a MosFet be tested in circuit?
Similarly one may ask, do MOSFETs fail open or closed?
The short answer is I would expect a MOSFETtofail as an open circuit due toover-temperatureconditions. This wikipedia article suggests that:Increase indrain-to-source resistance. Much of the MOSFETheating athigh currents is in the leads - which can quite easilyunsolderthemselves without the MOSFET failing!
Accordingly, how do you test a transistor in a circuit?
Hook the positive lead from the multimeter to the totheEMITTER (E) of the transistor. Hook the negative meterleadto the BASE (B) of the transistor. For an goodNPNtransistor, you should see “OL” (OverLimit).Ifyou are testing PNP transistor, the metershould showa voltage drop between 0.45V and 0.9V.
Connect the base terminal of the transistor totheterminal marked positive (usually coloured red) onthemultimeter. Connect the terminal marked negative orcommon(usually coloured black) to the collector and measuretheresistance. It should read open circuit (there should beadeflection for a PNP transistor).