Testing
a MOSFET device is simple. The leads show infinite resistance to each other
except for drain to source in one direction because of the presence
of a protection diode.
To
prove the device is functional:
- Connect the negative lead of the ohmmeter to the SOURCE lead.
- Touch the ohmmeter positive lead to the gate, to pre-charge it.
- Connect the ohmmeter positive lead to the DRAIN. If the device is good you will get a resistance reading of about 400-1k ohms. Some DVMs do not produce enough DC voltage in the ohms mode. The diode check mode can be used with these models. When using the diode mode, a low voltage drop is shown after pre-charging the gate.
