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MOS-FET TESTER CIRCUIT
Here are some steps to test a MOSFET by using
multitester.
Connect the 'Source' of the MosFet to the meter's negative (-) lead.
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Hold the MosFet by the case or the tab but don't
touch the metal parts of the test probes with any of the other MosFet's
terminals until needed. Do NOT allow a MOSFET to come in contact with your
clothes, plastic or plastic products, etc. because of the high static
voltages it can generate.
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First, touch the meter positive lead onto the
MosFet's 'Gate'.
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Now move the positve probe to the 'Drain'. You
should get a 'low' reading. The MosFet's internal capacitance on the gate
has now been charged up by the meter and the device is 'turned-on'.
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With the meter positive still connected to the
drain, touch a finger between source and gate (and drain if you like, it
does not matter at this stage). The gate will be discharged through your
finger and the meter reading should go high, indicating a non-conductive
device.
Another way to test a MOSFET is using a simple
circuit below. When 'GATE' is connected to positive voltage, then MOSFET
will act like a 'ON' switch, then LED will illuminate. If the LED do not
illuminate, so we can conclude that the MOSFET is broken.
Figure 1. Simple MOSFET Tester Circuit
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