09:09
Faizan
You can find discrete MOSFET transistors in audio, radio, power and other kinds of electronic circuits. These devices use a small input voltage to control currents. Below a threshold voltage of a few volts, they conduct practically no current. At a few volts past their threshold, they conduct strongly. MOSFETs come in P and N-channel types, each having enhancement and depletion mode varieties. You can test a MOSFET with a simple multimeter and battery setup, but you first need to know its type and mode.
Read the MOSFET's data sheet. It should describe the transistor's type and mode on the first page. Identify the transistor's source, drain and gate leads from the diagrams on the data sheet.
Turn the multimeter on and set its function knob to read resistance. If the meter is not an autoranging model, set the resistance range to "x100 ohms." If the MOSFET is a N-channel type, reverse the polarity of the probes for the purpose of this test.
Connect the wrist strap's grounding clip to a solid earth ground, such as an electrical conduit or equipment chassis ground. Slip the strap on your wrist.
Touch the multimeter's red probe to the transistor's source lead and the black probe to the gate lead. You should read infinite resistance on the meter.
Clip the jumper wire to the transistor's gate and source leads. Touch the multimeter's red probe wire to the transistor's source lead and the black probe to the drain lead. An enhancement-mode transistor will read infinite resistance on the meter. A depletion-mode transistor will read from a few ohms to a few hundred ohms. Disconnect the jumper wire.
Connect the 9-volt battery to the battery clip. If you have a P-channel MOSFET, clip the positive wire from the battery clip to the transistor's source lead. Clip the negative wire to the gate lead. If the transistor is N-channel, clip negative to source and positive to gate.
Touch the meter's red probe to the transistor's source lead and the black probe to the drain lead. An enhancement-mode device will give a resistance reading of a few ohms or less. A depletion-mode device will give resistance readings of very high to infinite ohms.
Discard the transistor if it has failed any of the preceding tests.
Read the MOSFET's data sheet. It should describe the transistor's type and mode on the first page. Identify the transistor's source, drain and gate leads from the diagrams on the data sheet.
Turn the multimeter on and set its function knob to read resistance. If the meter is not an autoranging model, set the resistance range to "x100 ohms." If the MOSFET is a N-channel type, reverse the polarity of the probes for the purpose of this test.
Connect the wrist strap's grounding clip to a solid earth ground, such as an electrical conduit or equipment chassis ground. Slip the strap on your wrist.
Touch the multimeter's red probe to the transistor's source lead and the black probe to the gate lead. You should read infinite resistance on the meter.
Clip the jumper wire to the transistor's gate and source leads. Touch the multimeter's red probe wire to the transistor's source lead and the black probe to the drain lead. An enhancement-mode transistor will read infinite resistance on the meter. A depletion-mode transistor will read from a few ohms to a few hundred ohms. Disconnect the jumper wire.
Connect the 9-volt battery to the battery clip. If you have a P-channel MOSFET, clip the positive wire from the battery clip to the transistor's source lead. Clip the negative wire to the gate lead. If the transistor is N-channel, clip negative to source and positive to gate.
Touch the meter's red probe to the transistor's source lead and the black probe to the drain lead. An enhancement-mode device will give a resistance reading of a few ohms or less. A depletion-mode device will give resistance readings of very high to infinite ohms.
Discard the transistor if it has failed any of the preceding tests.
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