The GATE Grind

GATE 2023 IN – Question 18

Communication and Optical Instrumentation · Optical sources and detectors · 1 mark · Multiple choice

An LED emits light when it is ______ biased. A photodiode provides maximum light sensitivity when it is ______ biased.

  1. forward, forward
  2. forward, reverse
  3. reverse, reverse
  4. reverse, forward

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Show answer and explanation

Correct answer: (B) forward, reverse

Explanation

Forward bias injects carriers into an LED for radiative recombination. Reverse bias widens the photodiode depletion region and efficiently collects photogenerated carriers. The pair is **forward, reverse, B**.