Semiconductor Questions

Multiple Choice Questions

Question 1
In a PN-junction diode not connected to any circuit
(a) The potential is the same everywhere
(b) The P-type is a higher potential than the N-type side
(c) There is an electric field at the junction directed from the N- type side to the P- type side
(d) There is an electric field at the junction directed from the P-type side to the N-type side

Question 2
Hole is
(a) an anti-particle of electron.
(b) a vacancy created when an electron leaves a covalent bond.
(c) absence of free electrons.
(d) an artificially created particle

Question 3
Which of the following statements is not true
(a) The resistance of intrinsic semiconductors decrease with increase of temperature
(b) Doping pure Si with trivalent impurities give P-type semiconductors
(c) The majority carriers in N-type semiconductors are holes
(d) A PN-junction can act as a semiconductor diode

Question 4
The conductivity of a semiconductor increases with increase in temperature because
(a) number density of free current carriers increases.
(b) relaxation time increases.
(c) both number density of carriers and relaxation time increase.
(d) number density of current carriers increases, relaxation time decreases but effect of decrease in relaxation time is much less than increase in number density.

Question 5
The depletion layer in the P-N junction region is caused by
(a) Drift of holes
(b) Diffusion of charge carriers
(c) Migration of impurity ions
(d) Drift of electrons

Question 6
In the depletion region of a diode
(a) there are no mobile charges
(b) equal number of holes and electrons exist, making the region neutral.
(c) recombination of holes and electrons has taken place.
(d) immobile charged ions exist.

Question 7
The AC current gain of a transistor is 120. What is the change in the collector current in the transistor whose base current changes by 100 $\mu A$ ?
a. 12 mA
b. 12 $\mu A$
c. 10 $\mu A$
d. 10 mA

Question 8
What is the majority charge carrier in p-type semiconductor?
a. Holes
b. electrons
c. Both equal
d. None of the above

Question 9
What is relation between power gain, voltage gain and current again of a transistor amplifier?
a. Power gain =Voltage gain/Current gain
b. Power gain =Voltage gain * Current gain
c. Current gain=Power gain * Voltage gain
d. Voltage gain= Current gain/Power gain

Question 10
What is the relationship between current gain $\alpha$ and $\beta$?
a. $\beta = \frac {\alpha}{1 - \alpha}$
b. $\beta = \frac {\alpha}{1 + \alpha}$
c. $\alpha = \frac {\beta}{1 - \beta}$
d. None of the above

Question 11
Consider an npn transistor with its base-emitter junction forward biased and collector base junction reverse biased. Which of the following statements are true?.
(a) Electrons crossover from emitter to collector.
(b) Holes move from base to collector.
(c) Electrons move from emitter to base.
(d) Electrons from emitter move out of base without going to the collector.

Question 12
When the P end of P-N junction is connected to the negative terminal of the battery and the N end to the positive terminal of the battery, then the P-N junction behaves like
(a) A conductor
(b) An insulator
(c) A super-conductor
(d) A semi-conductor

Question 13
In an n-type silicon, which of the following statement is true
(a) Electrons are majority carriers and trivalent atoms are the dopants.
(b) Electrons are minority carriers and pentavalent atoms are the dopants.
(c) Holes are minority carriers and pentavalent atoms are the dopants.
(d) Holes are majority carriers and trivalent atoms are the dopants

Text Based Questions(long)

Question 1
Explain the following:
(i) In the active state of the transistor, the emitter base junction acts as a low resistance while base collector region acts as high resistance.
(ii)Output characteristics are controlled by the input characteristics in common emitter transistor amplifier.
(iii)LEDs are made of compound semiconductor and not by elemental semiconductors.

Question 2
The graph of potential barrier versus width of depletion region for an unbiased diode is shown in A. In comparison to A, graphs B and C are obtained after biasing the diode in different ways. Identify the type of biasing in B & C and justify your answer.

Question 3
With proper diagram, explain the movement of charge carriers through different parts of the transistor and hence show that $I_E = I_B + I_C$.

Question 4
Draw a circuit diagram to study the input and output characteristics of an n-p-n transistor in its common emitter configuration.

Question 5
Draw the typical input and output characteristics and explain how these graphs are used to calculate current amplification factor of the transistor.

Question 6
Draw the circuit diagram of a full-wave rectifier and briefly explain its working principle.

Question 7
Explain how the depletion layer and barrier potential are formed in a p-n junction diode.

Question 8
Explain how p-n junction diode acts as Half wave rectifier and Full wave Rectifier

Question 9
Define the following terms
(a) Input resistance
(b) Output resistance.
(c) Current amplification factor $\beta$ of a transistor used in its CE configuration.

Short Answer type

Question 1
What is meant by the term doping of an intrinsic semiconductor ? How does it affect the conductivity of a semiconductor ?

Question 2
Give the logical symbol of an AND gate. Mark the inputs and outputs.

Question 3
Draw the logic symbol for a NAND gate.

Question 4
The output of an AND gate is connected to both the inputs of NAND gate. Draw the logic circuit of this combination of gates and write its truth table.

Question 5
The output of an OR gate is connected to both the inputs of a NAND gate. Draw the logic circuit of this combination of gates and write its truth table.

Question 6
Why are the NAND and NOR gates are known as Universal Gates?

Question 7
Write the Full form for the following
a. SSI
b. MSI
c. LSI
e. IC

Question 8
Draw the energy band diagrams of the below substances
a. Conductor
b. n- type semiconductor
c. p - type semiconductor
d. Insulator

Question 9
Give the symbol and truth table of each of the two logic gates ,obtained by using the two gate combinations as shown below
Semiconductor Important Questions for Class 12

Question 10
The output of an OR gate is connected to both the inputs of a NAND gate. Draw the logic circuit of the combination of gates and write its truth table

Match the Column

Question 1

Question 2

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