Download AKTU B-Tech 3rd Sem 2016-2017 NEC 302 Fundamental Of Electronic Devices Question Paper

Download AKTU (Dr. A.P.J. Abdul Kalam Technical University (AKTU), formerly Uttar Pradesh Technical University (UPTU) B-Tech 3rd Semester (Third Semester) 2016-2017 NEC 302 Fundamental Of Electronic Devices Question Paper

Printed Pages: 4 NEC-302
(Following Paper ID and Roll No. to be ?lled in your
I?apcr ll): 2012360 . Roll No,
Answer Books)
B.TECH
Regular theory Examination(0dd Sem - 111), 2016-17
FUNDAMENTAL OF ELECTRONIC DEVICES
T ime : 3 Hours 1 Max. Marks : 100
Section - A?
1 Attempt all parts. All parts carry equal marks. write
answer of each part in short. .(10X2=20)
a) Classify semiconductors on the basis of energy band
gap with the help of suitable diagram.
b) Calculate the density of GaAs, if the lattice conStant
of GaAs is 5.65 A0. The atomic weights ofGa and
As are 69.7 and 74.9 g/mol, respectively.
0) Differentiate between phosphorescence and
?orescence materials with examples.
d) What is population inversion? Write down the
difference between spontaneous emission and
, stimulated emission for LASER action.
e) Explain the V?I characteristics ofphotodiode. What
is the signi?cance of 3"] and 4th quadrant operation
' ofphotodiode?
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NEC-302
f) What is Fermi level? How does it depend on
temperature?
g) What is the physical signi?cance of diffusion
length? How is it related with mobility of the
carrier?
h) What do you mean by reverse recovery transient?
State the signi?cance of storage delay time.
i) What are degenerate semi-conductors? Draw their
energy band diagrams.
j) Calculate the maximum packing fraction of fee
lattice.
Section - B
Note: Attempt any ?ve questions from this section
(5X10=50)
2. a) What do you mean by mobility of a carrier? How
does it depend on temperature, doping
concentrations and high ?eld? Explain.
b) Mobilities of electrons and holes in a sample of
intrinsic germanium at room temperature are 3900
cmZ/v-sec and 1900 cmz/v-sec respectively. If the
electrons and hole densities are each equal to
2.5 x 10?3 per cm3, calculate germanium resistivity
and conductivity.
3. Discuss Transition and Diffusion capacitance in a p-n
junction diode. In a p? - n?junction reverse biased at 10V,
the capacitance is 10pF. If the doping is doubled and
reverse bias voltage is changed to 80V, what will be the
capacitance?
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NEC-302
a) A silicon sample is doped with 10'5 donors/cm3 and
has a hole life time of0.5 usec. Assuming all the
donors to be ionized, determine :
i) The photo generation rate, which will produce
4 x 104 excess EHP in steady state.
ii) The sample resistivity before and after
illumination.
iii) The percentage of conductivity due to
minority carriers. '
Assume ,u" = 1200 cmZ/Vs, up = 400 cmZ/V-s,
T = 300 K.
b) What do you mean by dri? and diffusion of carriers?
Find total current density generated due to both of
these transport mechanisms of carriers.
Using suitable diagrams, describe the principle and
operation of a Tunnel diode. Also discuss its V?l
characteristics.
Draw and explain the hole and electron ?ow in a p-n-p
Common Base BJT. State various currents ?owing across
the device along with characteristics curves.
Show that the total depletion width in a p-n junction at
thermal equilibrium condition can be given by
q Na Nd
Where 3 is the permittivity of semiconductor, V0 is the
built-in potential of the junction, Na is the acceptor
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NEC-302
concentration in the p-type-material, N d is the donor
concentration in the n-type material and q is the electronic
charge.
8. Derive an expression for diode current in an ideal p-n
junction diode
9. What 15 Hall effect? Derive the relation between Hall
4 voltage and carrier concentration. *
Section- C
Note: Attempt any two questions from this section
, (2X15=30)
10. Write the special features of MESFET Explain the
working of normally-off and normally-on MESFETS with
its characteristics
11. a) Derive the expression for the equilibrium carrier
concentration for holes using Fermi Dirac
distribution function.
b) A Si doped with 10] 7 per cm3 Boron atoms has fermi
level 0.36 eV above valence band at 300K. What is
the density of states in valence band?
12. Write short notes on :
a) LED materials;
b) GUNN Diode.
c) IMPATT Diode.
.++++
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