Schottky diode versus p–n diode Compared to a conventional p–n junction diode, a Schottky diode typically has:
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Alower cut-in voltage and lower reverse saturation current
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Bhigher cut-in voltage and higher reverse saturation current
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Clower cut-in voltage and higher reverse saturation current
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Dhigher cut-in voltage and lower reverse saturation current
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Esame cut-in voltage and zero reverse current
Answer
Correct Answer: lower cut-in voltage and higher reverse saturation current
Explanation
Introduction / Context:Schottky diodes form a metal–semiconductor junction rather than a p–n junction. They are widely used in high-speed switching power supplies due to their low forward drop and negligible reverse recovery charge.
Given Data / Assumptions:
- Forward “cut-in” (knee) voltage of Schottky ~ 0.2–0.4 V (Si), lower than p–n ~ 0.6–0.7 V.
- Reverse leakage of Schottky is typically higher than p–n of the same area and rating.
Concept / Approach:The barrier at a metal–semiconductor contact is lower than the built-in potential of a p–n junction, yielding a lower forward drop. However, the same structure provides fewer mechanisms to block reverse current tightly, resulting in higher leakage, especially at elevated temperatures.
Step-by-Step Solution:Compare forward conduction: Schottky has lower Vf → lower cut-in voltage.Compare reverse behavior: Schottky exhibits larger reverse saturation/leakage.Therefore, the correct pair is “lower cut-in voltage and higher reverse saturation current”.
Verification / Alternative check:Datasheets for power Schottky rectifiers specify low Vf and relatively high IR compared to ultrafast p–n diodes.
Why Other Options Are Wrong:
- (a) claims low leakage, which is not typical.
- (b) and (d) contradict the hallmark low forward drop.
- (e) reverse current is nonzero in real devices.
Common Pitfalls:
- Using Schottky diodes at high temperature without accounting for increased leakage.
- Assuming zero reverse recovery—there is very low charge, but not strictly zero dynamics.
Final Answer:lower cut-in voltage and higher reverse saturation current