Assertion and Reason on Reverse Biased Diode Characteristics
Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: A diode under reverse-biased condition provides very small current which is nearly independent of voltage until a critical limit at which the current increases drastically.
Reason R: Below the critical voltage limit, only majority charge carriers flow which increases drastically above critical voltage.
choose the correct answer from the options given below
Options
Both A and R are true and R is the correct explanation of A
Both A and R are true but R is NOT the correct explanation of A
A is true but R is false
A is false but R is true
Topics & Concepts
Step-by-Step Solution
To determine the correct option, let us analyze the Assertion and Reason separately:
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Analysis of Assertion A: In a p-n junction diode under reverse-biased conditions, the external applied voltage reinforces the built-in potential barrier, which repels the majority charge carriers away from the junction.
- Consequently, the current due to majority charge carriers becomes practically zero.
- However, a very small current, known as the reverse saturation current, flows across the junction due to the thermal generation of minority charge carriers (electrons in the p-side and holes in the n-side).
- This reverse saturation current is virtually independent of the applied voltage over a wide range.
- When the reverse voltage reaches a critical limit known as the breakdown voltage (), breakdown occurs (either Zener breakdown or Avalanche breakdown), resulting in a sharp and drastic increase in reverse current.
Therefore, Assertion A is true.
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Analysis of Reason R:
- Below the critical breakdown voltage, the reverse current is caused exclusively by the drift of minority charge carriers, not majority carriers.
- Majority carriers are restricted from crossing the junction due to the widened depletion layer and increased potential barrier under reverse bias.
Therefore, Reason R is false.
Conclusion: Since Assertion A is true and Reason R is false, the correct option is C.