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CS/B. TECH(N)/ODD/SEM-31346012022-2023/1019
MAULANA ABUL KALAM AZAD UNIVERSITY OF TECHNOLOGY, WEST BENGAL
Popor Codo : EC301 Eloclronlc Dovlcos
� UPID: 003460
Full Marks :70
Time Allotted : 3 Hours
/ndlc£1to full mmks.
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Group•A (Very Shorl Answer Typ
( 1 x 10"' 10 J
1. Answer any tcm of the following :
JV Which depletion layer of a BJT is wider?
\l.,lll· The speed of switching is les.s In MOSFETs.
(Un Absorption coefficient of a semiconductor __
Is a strong runclion or ___________
-0-M lonlc and covalent bonding are generally ________ lhan metallic bonding
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M· Total potential barrier of a pn junction dtode Is reduced in _____ mode
�o Which region of a BJT is most heavily doped? _., l:,'N\i -I �v..
(Vil) _______
is \he highest filled energy level of the electron al OK
<YJllnn a Schottky diode, normally uc-e <1,h'vt charged donor atoms remain In the space charge reglon.
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llXl Write the range of values for Common-Base current gain a.
�QC > "ln which MOSFET the channel becomes depleted of majority carriers for-Vos? ( (,,-, h.ttnu.,.,, �"' � P • c_ l,,,pt,'"' • I )
(XIJ How \he slope of the same?
current-voltage characleristic ol a pn diode is related to the small signal model of the
-B9V What is Early eHect?
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Group•B (Short Answer Type Ouesl/on)
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Answer any three of fhe following C
Explain the:co-niint'ifeiisiiyfor an .ideal pn junction and derive ii equations.
2, I5J
Draw the output characteristics of a transistor In common emitter (CE) mode. Show the ditterent regions on the I5l
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} output characteristics. Write the name/s of lhe region/s in which the transistor can be used as an amplifier and the
corresponding biasing conditions.
4- Describe the process of formation of energy bands in crystals. I 5I
5. From the one dimensional Poisson's equation ror electrlc field E, oblain the expression tor E in the n region of a ( 5I
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Schottky diode'
.§, • Draw the energy-band diagram in a p•lype semiconductor at the threshold inversion point and explain the (5]
formation of the inversion layer in the MOS capacitor.
Group-C (Long Answer Type Ouestlon)
Answer any three of the following ( 1 s x 3 • 45 J
7. (a) Derive the expression for total drift current densily in a semiconductor.
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Jb)' What are mobility and conductivity? Write the effects or temperature and doping on mobility.
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(c) Derive the one dimensional continuity equation for holes in a semiconductor. I 51
8. (a) Draw the ideal energy-band diagram of a pn junction under no bias, lorward bias and reverse bias. Explain all ( 3+4+4 J
the energy band diagrams.
(g),f'Draw the ideal energy-band diagram of a metal-semiconducto r junction under forward bias. Write the I4 1
advantage of Schottky diodes.
9. (a) Write the differences between zener breakdown and avalanche breakdown, I6I
{9Ybraw the circuit diagram _or a si�ple oltage regulator circuit using a zener diode and
_ � explain how the
regulation is obtain ed agains t variatio n in load current. Cs I
�Describe the planar process lor formation of a pn junction diode. (4J
1/2
10. (a) Draw the circuit diagrams for obtaining the input and output charac teristics or an npn transistor in common· r 4+5 J
emitter (CE) mode. Discuss the steps to operate those circuits and plot the characleristics.
(b) Whal are the current gains of a transistor? Derive the relation between them. £61
1,. (a) Derive and explain Iha expressions for excess minorily carriers in a pn ;unction as functions of distance. [SJ
(b) From the expression for built in potential ol·a pn junction diode find the expression for widlh of lhe space
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charge region under reverse bias.
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(c) Consider a silicon pn diode at T=300 K with doping c0ncentralions of Na-1016 cm-3 and Nd=10t5 cm-3.
Calculate the space charge width and electric field in the same.
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