Transistor Action
Hardphysics
In an n-p-n transistor, large collector current flows because:
Select the correct option:
Solution
Incorrect! Answer:
Thin base allows most injected electrons to reach collector
In an n-p-n transistor (operating in the active region):
- The emitter-base junction is forward biased, injecting a large number of electrons into the base.
- The base is made extremely thin and lightly doped.
- This ensures that only a tiny fraction (typically <2%) of these electrons recombine with holes in the base.
- Most electrons (>98%) diffuse across the base and are 'collected' by the reverse-biased collector junction, resulting in a large collector current (IC≈IE).
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About This Question
- Subject
- physics
- Chapter
- semiconductor electronics
- Topic
- transistor action
- Difficulty
- Hard
- Year
- 2025
Solution
Correct Answer:
Thin base allows most injected electrons to reach collector
In an n-p-n transistor (operating in the active region):
- The emitter-base junction is forward biased, injecting a large number of electrons into the base.
- The base is made extremely thin and lightly doped.
- This ensures that only a tiny fraction (typically <2%) of these electrons recombine with holes in the base.
- Most electrons (>98%) diffuse across the base and are 'collected' by the reverse-biased collector junction, resulting in a large collector current (IC≈IE).
This hard difficulty physics question is from the chapter semiconductor electronics, covering the topic of transistor action. It appeared in the 2025 exam.
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