Question
What causes a junction diode to fail from excessive current?
Answer Options
- A) Excessive inverse voltage
- B) Excessive junction temperature
- C) Insufficient forward voltage
- D) Charge carrier depletion
Correct Answer: B
Explanation
When a junction diode (or any semiconductor device) is conducting current, it possesses a forward voltage drop (typically 0.6 \text{ V} to 0.7 \text{ V} for silicon). The power dissipated by the diode is the product of the current flowing through it and this forward voltage drop (P = I \times V_F).
If the current becomes excessive, the power dissipation (P) rapidly increases, generating heat within the tiny junction. Since most semiconductor failures are thermal in nature, what causes a junction diode to fail from excessive current is excessive junction temperature. If the internal temperature exceeds the maximum safe limit (the thermal rating), the semiconductor material is permanently damaged, typically resulting in a short or open circuit.
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