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Electronics Engineering QUESTION #11694
Question 1
An IGBT gate-emitter is tested with a DMM diode check: forward voltage reads 0.4 V and reverse reads OL. Then collector-emitter (with gate floating) reads a low resistance. This means the IGBT is:
  • Functioning normally — the body diode is present
  • Shorted between collector and emitter — device is failed✔️
  • Operating in avalanche breakdown mode
  • A depletion-mode device and this is expected
Correct Answer Explanation
A healthy IGBT should show OL (open) between collector and emitter with the gate floating, because it is a voltage-controlled device that only conducts when gate voltage exceeds the threshold. A low resistance C-E reading with floating gate means the IGBT is permanently latched or shorted — the device is failed and must be replaced.