Power Electronics Multiple Choice Questions on “Types of Power Diodes-1”.
1. Shown below is the diagram of an ideal super diode. When the input voltage Vin is negative, then the output voltage Vout = ?
A. Vout/Vin
B. Vin
C. 0
D. Vin * Rl
Answer: C
Clarification: When the input voltage is negative, there would be a negative voltage on the diode so it works like an open circuit. Hence no current flows through the load and Vout is zero.
2. In order to reduce the reverse recovery time of the diodes, __________ is carried out.
A. shortening of the length of the device
B. platinum & gold doping
C. antimony doping
D. adding an extra silicon layer
Answer: B
Clarification: Platinum & gold doping improves the performance of the devices.
3. Which of the following diodes uses a metal-semiconductor junction?
A. General purpose diodes
B. Fast recovery diodes
C. Schottky diode
D. None of the mentioned
Answer: C
Clarification: Schottky diode uses a Al-Semiconductor junction.
4. Which of the below mentioned statements is false regarding Schottky diodes?
A. Schottky diodes have a Al-Silicon junction
B. There is no storage of charges in a Schottky diode
C. The majority charge carriers in a Schottky diode are holes
D. Schottky diodes can be switched off faster than a p-n junction diode of the same rating
Answer: C
Clarification: The majority charge carriers in a Schottky diode are electrons not holes.
5. A Schottky diode _____
A. has current flow due to holes only
B. has no reverse recovery time
C. has large amount of storage charges
D. has zero cut-in voltage
Answer: B
Clarification: Due to the metal-silicon junction there are no stored charges hence, no reverse recovery time, due to which the switching is faster.
6. Which of the following are/is the majority charge carriers in a Schottky diode?
A. Holes
B. Electrons
C. Both holes & Electrons carry equal current
D. None of the mentioned
Answer: B
Clarification: The metal has no holes hence major(almost full) current flows due to the electrons only.
7. In a Schottky diode, the silcon is usually
A. N-type
B. P-type
C. un-doped semiconductor
D. silicon is not used
Answer: A
Clarification: Usually only n-type silicon is used because the p-type has certain limitations.
8. As compared to a p-n junction diode(of the same rating), a Schottky diode has ___________
A. higher cut-in voltage
B. lower reverse leakage current
C. higher operating frequency
D. higher switching time
Answer: C
Clarification: Due to the metal-silicon junction there are no stored charges, hence no reverse recovery time due to which the switching is faster.
9. A Schottky diode has __________
A. a gate terminal
B. aluminum-silicon junction
C. platinum gold junction
D. germanium-Arsenide junction
Answer: B
Clarification: Schottky diode uses a Al-Semiconductor junction.
10. A Schottky diode can be switchd off much faster than an equivalent p-n junction diode due to its
A. higher operating frequency
B. no recombination of charges
C. more compact structure
D. None of the mentioned
Answer: B
Clarification: Due to the metal-silicon junction there are no stored charges, hence no reverse recovery time due to which the switching is faster.