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Chapter 14: Semiconductor Electronics: Materials, devices and Simple circuits
Frequency :
Sl.No.
1
( Asked three times or more )
Question
Marks Year
Draw a simple circuit of a CE transistor amplifier. Explain its working.
Show that the voltage gain AV, of the amplifier is given by
5
,where
is the current gain, RL is the load resistance and ri is the input
resistance of the transistor. What is the significance of the negative sign in
the expression for the voltage gain?
2
2012(D)
Questions of
similar
nature asked
in
2008,
2009
2006,
2013
Explain the function of base region of a transistor. Why is this region made
thin and lightly doped?
Draw a circuit diagram to study the input and output characteristics of
n-p-n transistor in a common emitter (CE) configuration. Show these
characteristics graphically. Explain how current amplification factor of the
transistor is calculated using output characteristics.
5
3
4
5
6
OR
(i) Draw a circuit diagram to study the input and output characteristics of
an n-p-n transistor in its common emitter configuration. Draw the typical
input and output characteristics.
(ii) Explain, with the help of a circuit diagram, the working of n-p-n
transistor as a common emitter amplifier.
(i) With the help of circuit diagrams distinguish between forward biasing
and reverse biasing of a p-n junction diode.
(ii) Draw V-I characteristics of a p-n junction diode in (a) forward bias, (b)
reverse bias.
(a) Why is zener diode fabricated by heavily doping both p-and n-sides of
the junction?
(b) Draw the circuit diagram of zener diode as a voltage regulator and
briefly explain its working.
OR
How is a zener diode fabricated so as to make it a special purpose diode?
Draw I-V characteristics of zener diode and explain the significance of
breakdown voltage.
OR
Name the semiconductor device that can be used to regulate an unregulated
dc power supply.With the help of I-V characteristics of this device, explain
its working principle.
Draw a circuit diagram of a full-wave rectifier. Explain its working
principle.
Draw the input/output wave-forms indicating clearly the functions of the
two diodes used.
Explain, with the help of suitable diagram, the two important processes that
2009(D)
3
3
2009,
2010,
2014(D)
2008,
2009,2010(F)
2012,
2014(F)
2009(D)
2
2011(D)
3
3
2007,
2008,2012
2009,
2
2010,
2012,
2015
2010
2
2013(D)
3
2014(F)
2
2010(AI)
2
2008(D)
2
2010(AI)
2
2011(D)
occur during the formation of p-n junction. Hence define the terms :
depletion region and barrier potential.
7
8
Draw the circuit diagram of an illuminated photodiode in reverse bias.
How is photodiode used to measure light intensity?
OR
Explain, with the help of a circuit diagram, the working of a photo-diode.
Write briefly how it is used to detect the optical signals.
OR
(a) How is photodiode fabricated?
(b) Briefly explain its working. Draw its V–I characteristics for two
different intensities of illumination.
(i)
Identify the logic gates marked P and Q in the given logic
circuit.
(ii)
Write down the output at X for the inputs A = 0, B = 0 and A
=1, B =1.
OR
The given inputs A, B are fed to a 2-input NAND gate. Draw the output
wave form of the gate.
OR
(iii)
Identify the logic gates marked P and Q in the given logic
circuit.
(ii)
Write down the output at X for the inputs A = 0, B = 0
and A =1, B =1.
OR
Write the truth table for the logic circuit shown below and identify the logic
operation performed by this circuit.
In the circuit shown in the figure, identify the equivalent gate of the circuit
and make its truth table.
2
2013(AI)
2
2014(D)
2
2014(D)
OR
Write the truth table for the combination of the gates shown. Name the gates used.
OR
Identify the logic gates marked ‘P’ and ‘Q’ in the given circuit. Write the truth
table for the combination.
Frequency :
Sl.No.
1
( Asked two times )
Question
(a) Draw the circuit diagram of a base-biased n-p-n transistor in C-E
configuration. Explain how this circuit is used to obtain the transfer
characteristic (Vo –Vi characteristics).
(b) The typical output characteristics (IC –VCE ) of an n-p-n transistor in
C-E configuration is shown in the figure. Calculate (i) the output
resistance r0 and (ii) the current amplification factor 𝛽ac .
Marks Year
5
2010,
2013
2
3
4
5
6
Explain, with the help of a circuit diagram, the working of a p-n junction
diode as a half-wave rectifier.
The current in the forward bias is known to be more (~mA) than the current
in the reverse bias (~µA). What is the reason, then, to operate the photodiode
in reverse bias?
Mention the important considerations required while fabricating a p-n
junction diode to be used as a Light Emitting Diode (LED). What should be
the order of band gap of an LED if it is required to emit light in the visible
range?
OR
How is a light emitting diode fabricated ? Briefly state its working. Write
any two important advantages of LEDs over the conventional incandescent
low power lamps. OR
Explain, with the help of a schematic diagram, the principle and working of a
Light Emitting Diode. What criterion is kept in mind while choosing the
semiconductor material for such a device ? Write any two advantages of
Light Emitting Diode over conventional incandescent lamps.
What are energy bands? How are these formed? Distinguish between a
conductor, an insulator and a semiconductor on the basis of energy band
diagram. OR
Draw energy band diagrams of an n-type and p-type semiconductor at
temperature T > 0 K. Mark the donor and acceptor energy levels with their
energies. OR
Distinguish between a metal and an insulator on the basis of energy band
diagrams.
3
What happens to the width of depletion layer of a p-n junction when it is (i) forward
biased, (ii) reverse biased?
2
2
2006,
2014
2008 ,2012
2
2013,
2015
3
2015(Bhubaneswar)
3
2007(D)
5
2006(AI)
2
2014(F)
2
2011(AI),2008(AI)
Frequency :
( Asked Once )
Sl.No.
Question
Marks Year
2006(D)
Draw a circuit diagram for use of NPN transistor as an amplifier in common 3
01
emitter configuration. The input resistance of a transistor is 1000Ω. On
changing its base current by 10µA, the collector current increases by 2 mA.
If a load resistance of 5kΩ is used in the circuit, calculate:
(i) The
Current
gain
(ii) voltage gain of the
amplifier
(a) Differentiate between three segments of a transistor on the basis of their
size and level of doping.
(b) How is a transistor biased to be in active state?
(c) With the help of necessary circuit diagram, describe briefly how n-p-n
transistor in CE configuration amplifies a small sinusoidal input voltage.
Write the expression for the ac current gain.
5
2014(D)