Summary & 50 MCQs with Answers
This chapter covers semiconductors, intrinsic and extrinsic materials, PN junction, diode characteristics, transistor operation, logic gates, and applications in electronics. It explains energy bands, carrier movement, rectification, and amplification principles.
1. Semiconductor materials have:
A) Conductivity between conductors and insulators ✅
B) Zero conductivity
C) Same conductivity as metals
D) Infinite conductivity
2. Intrinsic semiconductor is:
A) Pure semiconductor ✅
B) Doped with donor atoms
C) Doped with acceptor atoms
D) Metal
3. Extrinsic semiconductors are:
A) Doped semiconductors ✅
B) Pure semiconductors
C) Insulators
D) Metals
4. N-type semiconductor has:
A) Electrons as majority carriers ✅
B) Holes as majority carriers
C) Equal electrons and holes
D) Only protons
5. P-type semiconductor has:
A) Holes as majority carriers ✅
B) Electrons as majority carriers
C) Only neutrons
D) Equal electrons and holes
6. PN junction diode conducts when:
A) Forward biased ✅
B) Reverse biased
C) No bias
D) Both directions
7. Forward bias means:
A) P connected to positive and N to negative ✅
B) P to negative, N to positive
C) Both to positive
D) Both to negative
8. Reverse bias diode:
A) Blocks current ✅
B) Conducts current
C) Emits light
D) Acts as battery
9. Zener diode is used for:
A) Voltage regulation ✅
B) Amplification
C) Switching only
D) Rectification only
10. Transistor can be used as:
A) Amplifier and switch ✅
B) Only switch
C) Only amplifier
D) Battery
11. Energy band gap of intrinsic semiconductor at room temperature is:
A) 1–1.5 eV ✅
B) 0.1 eV
C) 5 eV
D) 3 eV
12. Majority carriers in N-type semiconductor are:
A) Electrons ✅
B) Holes
C) Protons
D) Neutrons
13. PN junction forms a depletion region because:
A) Electrons and holes recombine ✅
B) Neutrons are emitted
C) Current flows freely
D) Metal is inserted
14. Diode acts as:
A) Rectifier ✅
B) Amplifier
C) Battery
D) Resistor
15. Forward voltage of silicon diode is approximately:
A) 0.7 V ✅
B) 0.3 V
C) 1.5 V
D) 5 V
16. Forward voltage of germanium diode is approximately:
A) 0.3 V ✅
B) 0.7 V
C) 1 V
D) 1.5 V
17. Zener diode is used in:
A) Reverse bias ✅
B) Forward bias
C) Both directions
D) None
18. Breakdown voltage of Zener diode is:
A) Reverse bias voltage where it conducts ✅
B) Forward voltage
C) Zero voltage
D) Forward bias cutoff
19. Transistor has:
A) Three terminals: Emitter, Base, Collector ✅
B) Two terminals
C) Four terminals
D) One terminal
20. A transistor can be used as:
A) Amplifier ✅
B) Resistor
C) Battery
D) Capacitor
21. Common types of transistors are:
A) NPN and PNP ✅
B) ABC and XYZ
C) MOS and CMOS only
D) Diode and Triode
22. Biasing in transistor is used to:
A) Set proper operating point ✅
B) Connect battery
C) Change terminals
D) Emit photons
23. Amplification in transistor occurs due to:
A) Small base current controlling large collector current ✅
B) Large base current controlling collector
C) Equal currents
D) None
24. Logic gates are implemented using:
A) Transistors ✅
B) Diodes only
C) Resistors
D) Capacitors
25. AND gate output is HIGH when:
A) Both inputs are HIGH ✅
B) Either input is HIGH
C) Both inputs are LOW
D) One input is LOW
26. OR gate output is HIGH when:
A) Any input is HIGH ✅
B) Both inputs LOW
C) Both inputs HIGH
D) No input
27. Diode rectifier converts:
A) AC to DC ✅
B) DC to AC
C) AC to AC
D) DC to DC
28. Half-wave rectifier uses:
A) One diode ✅
B) Two diodes
C) Three diodes
D) None
29. Full-wave rectifier uses:
A) Two or four diodes ✅
B) One diode
C) Three diodes
D) None
30. Ripple factor in ideal rectifier is:
A) Zero ✅
B) One
C) Infinity
D) 0.5
31. A photodiode converts:
A) Light into current ✅
B) Current into light
C) Voltage into light
D) Heat into current
32. LED emits light when:
A) Forward biased ✅
B) Reverse biased
C) No bias
D) Both directions
33. Energy band diagram for N-type shows:
A) Donor level near conduction band ✅
B) Acceptor near valence band
C) No levels
D) Forbidden levels only
34. Energy band diagram for P-type shows:
A) Acceptor level near valence band ✅
B) Donor near conduction
C) Forbidden only
D) Intrinsic only
35. Majority carriers in P-type semiconductor are:
A) Holes ✅
B) Electrons
C) Protons
D) Neutrons
36. Minority carriers in N-type semiconductor are:
A) Holes ✅
B) Electrons
C) Protons
D) Neutrons
37. Minority carriers in P-type semiconductor are:
A) Electrons ✅
B) Holes
C) Protons
D) Neutrons
38. Reverse saturation current in diode:
A) Small and nearly constant ✅
B) Large
C) Zero
D) Infinite
39. Avalanche breakdown occurs due to:
A) Impact ionization ✅
B) Recombination
C) Forward bias
D) Forward current
40. Zener diode operates in breakdown region:
A) Reverse bias ✅
B) Forward bias
C) Zero bias
D) Both directions
41. Amplification factor of transistor in CE configuration is:
A) High ✅
B) Low
C) Zero
D) Negative
42. Input resistance of CE transistor is:
A) Low ✅
B) High
C) Infinite
D) Zero
43. Output resistance of CE transistor is:
A) High ✅
B) Low
C) Zero
D) Negative
44. Logic NOT gate output is:
A) Inverted input ✅
B) Same as input
C) Always HIGH
D) Always LOW
45. Logic NAND gate output is:
A) Inverted AND ✅
B) OR output
C) XOR output
D) NOR output
46. Logic NOR gate output is:
A) Inverted OR ✅
B) AND output
C) XOR output
D) NAND output
47. Semiconductor diode is made of:
A) Silicon or germanium ✅
B) Copper
C) Aluminium
D) Gold
48. Forward current of diode is mainly due to:
A) Majority carriers ✅
B) Minority carriers
C) Neutrons
D) Protons
49. Minority carrier injection occurs in:
A) Forward biased PN junction ✅
B) Reverse biased PN junction
C) Both biases
D) None
50. Rectifier output can be smoothed using:
A) Capacitor ✅
B) Resistor
C) Diode alone
D) Transistor