I am in the process of checking if my SiC mosfet is damaged or not. To do that, I take a multimeter and measure resistance between Drain and Source. The resistance starts with an order of 10M but increases upto 70 M and keep going. Am i right in thinking that this is because the output capacitance is getting charged with multimeter ion turn increasing the resitance? Also, when I check the voltage between Drain and Source, the reading is 2.2 V going down, So I remove the multimeter, put it back again and it starts again from 2.2 V (even after discharging with an external resistor of 110 ohms). Please help me understand what is happening

  • \$\begingroup\$ To properly check the functionality of a MOSFET you need more than only a multimeter. The only thing you can check with a multimeter is the diode between drain and source. If you have a known good MOSFET then you could also compare the behavior. If it is different then one is broken. Even if there is no difference than that's still no guarantee that the MOSFET is OK. \$\endgroup\$ Nov 21, 2017 at 9:35
  • \$\begingroup\$ I check the regular NMOSFETs with the following method: First, I ground myself for potential ESD and touch all the pins to the Earth so that any charges go away. Then I take the MOSFET on an isolated surface, take the DMM to Diode mode then touch the probes to the D-S first for checking body diode. If it does not show a short, I check the G-S just like checking the B-E junction of a BJT. This charges up the G-S capacitor and turns the MOSFET on for a short time. Before G-S cap discharges, I check the D-S on "short circuit" mode. If it shows a short, then it's OK. Hope this works on SiC ones. \$\endgroup\$ Nov 21, 2017 at 9:49
  • \$\begingroup\$ @ Rohat Kılıç Good information, put it up as answer for posterity. It does not technically answer the question but is highly relevant. \$\endgroup\$
    – RoyC
    Nov 21, 2017 at 10:23


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