MCQs on Semiconductor | Updated Pdf

Multiple Choice Questions on Semiconductors pdf 

Hello Students, how are you all hope you all will be good, in this Page we have shared with you more than 50 Important MCQ on Semiconductor which is helpful for verious entrance exams preparation. This Multiple Choice Questions on Semiconductors pdf will help you enhance your performance in entrance exams like NEET and JEE. Before starting Semiconductor MCQs know the What js semiconductor.

On the basis of band theory of solids, the substances are divided into three groups

(i) conductors

(ii) semi conductors

(iii) Insulators 

In an atom, the upper most empty energy band is called the Conduction band. The lowest completely filled energy band is called the Valence band. The forbidden band lies between the conduction band and the valence band. The electrons are forbidden to occupy it. The difference in the energy levels of conduction and energy bands is called the forbidden energy gap. For conductors it is practically zero. For insulators it is very large 5 to 15 eV). For semiconductors it is about 1 eV.

Semiconductors, without any impurity, are called intrinsic semiconductors. Examples Pure Germanium (Atomic weight 32) and pure Silicon (Atomic weight 14). Both are tetravalent. Intrinsic semiconductors, holes and electrons are Produced simultaneously and they act as charge carriers. In metals free electrons are the charge carriers. 


Mcqs on Semiconductor


Read : Physics MCQs


Multiple Choice Questions on Semiconductors pdf 

1. The energy gap between the conduction bond and valence band of a substance is of the order of 0.7 eV, then the substance is_______

(a) a conductor

(b) a semiconductor

(c) an insulator

(d) a super conductor

Answer : B


2. At ordinary temperature, an increase in temperature, increases the conductivity of_______

(a) a semiconductor

(b) a conductor

(c) a super conductor

(d) an insulator

Answer: A


Read : Solar Cell MCQs 


3. The energy band gap is maximum in__________

(a) copper

(b) an insulator

(c) gernmanium

(d) a super conductor

Answer: B


4. Fermi energy is the____

(a) minimum energy of electrons in a metal at 0 K

(b) maximum energy of electrons in a metal at 0 K

(c) minimum energy of electrons in a metal at 0° C

(d) maximum energy of electrons in a metal at 0° C

Answer: B


5. The valence band and the conduction band of a substance overlap at ordinary temperatures. The substance may be_____

(a) ap-type semiconductor

(b) a conductor

(c) an insulator

(d) an n-type semiconductor

Answer: B


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6. In an insulator_____

(a) the valence band is partially filled with electrons

(b) conduction band is partially filled with electrons

(c) conduction band is empty and the valence band is filled with electrons

(d) conduction band is filled with electrons and valence band is empty

Answer: C


7. When an n-n-p transistor is used as an amplifier, then______

(a) holes move from emitter to base

(b) electrons move from base to collector

(c) electrons move from collector to base

(d) electrons move from base to emitter

Answer: B


8. The electrical conductivity of a semiconductor increases When electromagnetic radiation of wavelength shorter than 2500 nm is incident on it. What is the band gap energy in eV for the semiconductor ? [h = 6.63 x 10‐³⁴ J-s]

(a) 0.9 eV

(b) 1.2 eV

(c) 1.8 eV

(d) 0.5 eV

Answer: D


9. A solar cell is basically a_____

(a) ap-type Ge semiconductor

(b) an illuminated n-p-n type transistor

(c) an intrinsic silicon semiconductor

(d) an illuminated silicon p-n junction diode

Answer: D


10. A potential barrier of 0.5 V exists across a p-n junction. What is the width of the depletion region if a constant electric field of magnitude 10⁵ V/m exists in the depletion region ?

(a) 3 umn

(b) 5 um

(c) 7um

(d) 4 um

Answer: B


Read : MCQs on Newton's Law of gravitation 


11. When the conductivity of a semiconductor is only due to breaking of covalent bonds, the semiconductor is called_____

(a) an n-type semiconductor

(b) ap-type semiconductor

(c) an intrinsic semiconductor

(d) an extrinsic semiconductor

Answer: B


12. In a transistor amplifier, the collector current is 5.5 mA for an emitter current of 5.6 mA. What is the current amplification factor of the transistor?

(a) 45

(b) 50

(c) 55

(d) 60

Answer: D


13.  If three amplifiers each with a gain of 5 are connected in series, then the overall amplification will be________
(a) 15
(b) 125
(c) 5/3
(d) 25
Answer: B


14. A NOR gate gives_____
(a) high output when both inputs are high
(b) high output when both inputs are low
(c) low output when both inputs are low
(d) high output when one input is low and the other input is high.
Answer: B


15. The potential barrier of a semiconductor is 0.6 V at room temperature. What is the approximate value of its potential barrier, if the temperature is increased by 20°C?
(a) 0.7 V
(b) 0.8 V
(c) 1.00 V
(d) 0.5 V
Answer: D


16. When a p-n junction diode is forward biased, the flow of current across the junction is mainly due to_____
(a) drifting of charges
(b) diffusion of charges
(c) both drift and diffusion of charges
(d) minority charge carriers
Answer: B


17. The inverter is_____
(a) an OR gate
(b) A NOT gate
(c) an AND gate
(d) a combination of OR and AND gates
Answer : B


18. In logic gates the bar sing, indicates_____
(a) OR operation
(b) AND operation
(c) NOT operation
(d) a universal gate
Answer: C


19. Consider the following statements A & B and identify the correct answer.
(A) A zener diod should be connected in reverse bias for proper functioning.
(B) The potential barrier of a p-n junction lies between 2 V and 5 V
(a) Both A & B are correct
b) Both A & B are wrong
(c) A is wrong and B is correct
(d) A is correct but B is wrong
Answer: D


20. The current obtained from a filterless rectifier is_____
(a) an eddy current
(b) sinusoidal current
(c) varyıng direct current 
(d) constant direct current
Answer: C 


22. A donor impurity_____
(a) increases the resistance of the semiconductor
(b) produces energy bands above the valence bands
(c) produces n type semiconductors
(a) produces p type semiconductors
Answer: C


23. In a bstance the energy gap between the conduction band and the valence band is 0.001 eV. The substance must be______
(a) an insulator
(b) a semiconductor
(c) an alloy
(d) a conductor
Answer : D


24. A transistor is essentially a_______
(a) voltage operated device
(b) resistance operated device
(c) current operated device
(d) power operated device
Answer: C


25. The dominant contribution to current comes from hols in the case of______
(a) metals
(b) intrinsic semiconductors
(c) p type extrinsic semiconductor 
(d) n type extrinsic semiconductor 
Answer: C


265. For which logic gate the following statement is true ? All low inputs produce a high output.______
(a) OR
(b) AND
(c) NAND
(d) NOT
Answer : C


26. For which logic gate the following statement is true ? The output is high, if and only if all inputs are high________
(a) AND
(b) OR
(c) NAND
(d) NOR
Answer: A


27. The truth table of a logic gate is a table______
(a) giving only the true numbers
(b) rejecting only the wrong numbers
(c) giving the relation-between the input and output variables of a logic gate
(d) which gives all the possible input logic levels and the corresponding resultant logic levels in the output.
Answer: D


28. For a two input logic gate, the truth table has 4 possible.input combinations. For a 3 input logic gate the number of combinations (entries) in the input side of the truth table are_______
(a) 4
(b) 6
(c) 8
(d) 10
Answer : C


29. The logic expression y = ABC is read as________
(a) y is equal to A plus B plus C
(b) yis equal to A or B or C
(c) y is equal to A and B and C
(d) y is equal to A dot B dot C
Answer: C


30. What is the current gain for a transistor used as a common emitter amplifier, if the current gain of the same transistor  used in common base mode is 0.95 ?
(a) 25
(b) 49
(c) 19
(d) 15
Answer : C


31. Transistors are prepared from_____
(a) metals
(b) insulators
(c) intrinsic semiconductors
(d) doped semiconductors
Answer : D


32. The difference in the working of a step up transrom and an amplifier is______
(a) the transformer decreases the power whereas tne.amplifier keeps the power constant
(b) the transformer increases the power but the ampiner decreases the power
(c) the amplifier increases the power but the transformer cannot inerease the power
(d) the amplifier decreases the power but the transformer keeps the power constant
Answer : C


33. Find the 'wrong' component from the following An electronic oscillator consists of________
(a) an amplifier
(b) a tank circuit or oscillating circuit
(c) externally applied input signal
(d) feedback network
Answer: C


34. Which is the 'wrong' statement from the following ?
In an clectronic oscillator, the positive feedback voitage
(a) increases the input voltage
(b) is always in phase with the input voltage
(c) is always in antiphase or 18O" out of phase with the input voltage
(d) transfers a part of the output energy of the amplifier to the resonating L-C circuit
Answer: C


35. To obtain the current gain (6) of a transistor, when it is in CE mode, we use_______
(a) its input characteristics
(b) its current transfer characteristics
(c) its output characteristics
(d) any one of the above three characteristics
Answer: B


36. A transistor is a_______
(b) a resistance device
(a) a voltage device
(c) a current device
(d) an inductive device
Answer : C


37. When the electrons leave the n material and enter the P material to fill up the holes, the process is called_________

(a) mixing

(b) diffusion

(c) doping

(d) depletion

Answer : B


38. When ap-njunction diode is forward biased it acts like_____

(a) a high resistance

(b) an ON switch

(c) an OFF switch

(d) a capacitor

Answer : B


39. In a halfwave rectifier, the output frequency is 50 Hz if the input frequency is 50 Hz. What is the output frequency of a fullwave rectifier for the same input frequency ?

(a) 50 Hz

(b) 100 Hz

(c) 25 Hz

(d) 75 Hz

Answer: B


40. When the resistance between p andn regions is very high then the p-n junction diode acts as_______

(a) an inductor

(b) a transistor

(c) a capacitor

(d) zener diode

Answer : C


41. Electric current is due to drift of electrons in_______

(a) metallic conductors

(b) semiconductors

(c) in both (a) and (b)

(d) insulators

Answer : C


42. If in ap-n junction diode, the drift current is less than the diffusion current in magnitude, then________

(a) p-njunction is reverse biased

(b) p-njunction is forward biased

(c) P-njunction is unbiased

(d) p and n regions are heavily doped

Answer: B


43. In a p- njunction, electric conduction takes place due to_______

(a) drift

(b) diffusion

(c) drift and diffusion

(d) barrier potential

Answer: C


44. When an ideal junction diode is reverse biased_______

(a) it acts like a short circuit

(b) it acts like a super conductor

(c) it acts like an open circuit

(d) it has a zero resistance

Answer: C


45. When an ideal junction diode is forward biased_____

(a) it acts as an open circuit

(b) it acts as a short circuit

(c) it acts as an insulator

(d) it has an infinite resistance

Answer: B


46. Zener breakdown Occurs only when______

(a) it is lightly doped

(b) the temperature is increa

(c)it is forward biased

(d) it is reverse biased

Answer: D


47. For the proper functioning of a zener diode as a voltage stabiliser it should be alway________

(a) forward biased

(b) reverse biased

(c) lightly doped

(d) connected in series with the load resistance

Answer : B


48. The value or tne zener current_______

(a) is determined by the zener voltage

(b) is always in the a microampere range

(c) does not depends upon the temperature

(d) is limited by the external circuit resistance

Answer : D


49. An LED is a_________

(a) forward biased p - njunction diode

(b) reverse biased p --n junction diode

(c) photodiode

(d) pin diode

Answer : A


50. The colour of light emitted by a LED depends upon______

(a) its forward bias

(b) its reverse bias

(c) the material of the semiconductor

(d) the amount of forward or reverse current

Answer: C


51.Once a zener diode is taken in its breakdown region, there Is not much change in its______

(a) current

(b) resistance

(c) voltage

(d) capacitance

Answer : C


52. Cneral purpose diode is more likely to suffer avalanche breakdown rather than zener breakdown because______

(a) its leakage current is small

(b) it has low reverse resistance

(c) it has strong co-valent bonds

(d) it is lightly doped

Answer: D


Hope this Multiple Choice Questions on Semiconductors pdf will helpful for your exams. mcqs on Semiconductors is a important topic in physics on which definitely one to two questions are come in exam. We also provide semiconductor mcq with answers pdf format.


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