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1. B.Tech. IVSemester(Back) Examination, June/July - 201 5
Electrical Engg.
4EEl Power Electronics - Il
o
Fl
N
trl
s
Instructions to Candidates:
Attempt any live questions, selecting one questittn.from esch unit. All questiolts
carryequalmarks.(Schentaticdiagramsmustbeshownwhereyernecessan'.
An1, daia you feel missing suitably be asstuned ond stated clearly. Units of
quantities used/calculated must be stated clearly.
Time : 3 Hours Maximum Marks : 80
Min. Passing Marks : 24
Unit.- I
1. a) Give briefamount ofdifferent feedback topologies. (8)
b) In a negative feedback arnplifieq the gain without feedback is 100, feedback
f'actor is B is 1125 and input voltage is 50 mv Calculate
i) Gain with feedback
ii) Feedback factor
iii) Feedback voltage
iv) Output voltage {2+2+2+2)
oR.
I . a) Drive expression for output rrsistance in voltage series feedback amplifier.
{8)
b) An RC corryled arnplifior hes a vdtags gain of 1000 f,:50H2, f":200KHzand
a distortion of 5Yo q,itlmut feedback. Find the amplifier voltage gain, Lower
and uppr &cquencies ard distortion when a negative feedback is applied
(8)with fee&ckratio0.Ol
Unit - II
2. a) Sketch a schmittrigger. Circuit and Explain its working priociple' {S)
b) Explain the Backhausen criterion for sustained oscillatisns. Draw tlre RC phase
shift oscillator circuit and Describe its workirry. (8)
4E2109 /zors (r ) {Contd-..

2. OR
Write short note on Bistable rnnltivibrator.2. a)
b)
(8)
In.a Traniistorised Hartley oscitlator if Lr=O.lmH, L,:lgpH and mutual
inductance between coil = 20 p H,
$ly!!1!e value ofCapacitor C, ofoscillatory circuit to obtain the frequetrcy.
of 4l l0 KHz (E)
Unit - EI
3. a) Describe function of an Op-Amp as.
r) Inverter
ii) Scalechanger
iii) Integrator
iv) Differerrtiator. (Z+Z+2+Z|
b) A 5 mv, I KHz sinusoidal signar is applied to the input of an op-amp inregrator
for. Which B=100 kdt andC =tttF . Find the output voltage. (S)
OR
3. a) Explain logarithmic and antilog amplifier using Op_Amp.
b) Describe the characteristic of an ideal Op_Amp.
Unit- IV
(8)
(8)
4. a) Explain an Astable multivibrator using 555 IC. (S)
b) In Fig- l calculate the purse width ofpositive negative purses and carculate the
free running frequency. (S)
.+ t". ,
f 1L
s.*f,*
f/'
&&:
J,oi-q r-
.J I1210* (2)

3. OR
Unit- Y
5. a) Elplain the general features ofaudio power amplifiers. Also explain the working
of class Apower amplifier (S)
b) A power transistor operated in class A operation delivers a maximtm of 6w to
a 8ct load with the supply voltage of 25V. The e point is adjusted for a
symmetrical swing calculate
i) Step down tum ratio.
ii) Peak calculator current
iii) Efficiency. (2+3+3)
OR
5' a) what is meant by cross over distortion is class-B amplifier. Explain how it is
overcome in class AB operation (E)
b) A class B push full amprifier hu vr.=50V The collector voltage swings from
V.. down to lOv with input signaliif the transistors used an m"axirnr;;;*".
dissipation rating of 20w,
4. Write down short note on any two
a) Peak detector
b) Regulatedpowersupplies
c) Ato D converter. (8+8)
(3+3+2)
Calculate
i) Load presented by output transformer.
ii) . Power output.
iii) D.C. power input.
482109 (3)