Question Paper: Basic Electronics : Question Paper Jun 2014 - First Year Engineering (C Cycle) (Semester 1) | Visveswaraya Technological University (VTU)
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Basic Electronics - Jun 2014

First Year Engineering (C Cycle) (Semester 1)

TOTAL MARKS: 100
TOTAL TIME: 3 HOURS
(1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks.


Choose the correct answer for the following :-

1 (a) (i) Zener diode can be used for rectification. This statement is ______
(A) True
(B) false
(C) neither true nor false
(D) noe of these
(1 marks)
1 (a) (ii) The maximum efficiency of full wave rectifier is _____
(A) 40.6%
(B) 60.4%
(C) 78.5%
(D) 81.2%
(1 marks)
1 (a) (iii) The knee voltage of a silicon diode is ______
(A) 0.3V
(B) 0.5V
(C) 0.7V
(D) none of these
(1 marks)
1 (a) (iv) If f Hz is the frequency of the input given to a half wave rectifier, the output frequency will be
(A) 2f Hz
(B) f Hz
(C) 3f Hz
(D) 0.5f Hz
(1 marks)
1 (b) Draw and explain the VI-characteristics of a Si-diode and Ge-diode.(6 marks) 1 (c) With a neat circuit diagram, explain the working principles of full wave bridge rectifier and show that the ripple factor=0.48, and efficiency = 81.2%(10 marks)


Choose the correct answer for the following :-

2 (a) (i) The current conduction in BJT is because of _____
(A) electrons
(B) holes
(C) both electrons and holes
(D) none of these
(1 marks)
2 (a) (ii) If &alph;=0.95, then the values if ? of transistor is _____
(A) 0.05
(B) 19
(C) 100
(D) 120
(1 marks)
2 (a) (iii) Common collector arrangement is generally used for _____
(A) impedance matching
(B) voltage amplification
(C) current amplifier
(D) none of these
(1 marks)
2 (a) (iv) The current relationship between two current gain in a transistor is _____
$$ (A) \ \beta =\dfrac {\alpha}{1- \alpha} \$$B) \ \beta=\dfrac {1+\alpha }{1-\alpha}\$$C) \ \beta = \dfrac {1-\alpha}{1+\alpha}\$$D) \ \beta = \dfrac {1+\beta}{\beta}\\$$\lt/span\gt\ltspan class='paper-ques-marks'\gt(1 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt2 (b)\lt/b\gt Draw input and output characteristics of an NPN transistor in common base configuration and explain.\lt/span\gt\ltspan class='paper-ques-marks'\gt(10 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt2 (c) \lt/b\gt For a Silicon transistor ?\ltsub\gtdc\lt/sub\gt=0.995, emitter current is 10 mA and leakage current I\ltsub\gtco\lt/sub\gt is 0.5?A. Find I\ltsub\gtc\lt/sub\gt, I\ltsub\gtB\lt/sub\gt, &beata; and I\ltsub\gtCEO\lt/sub\gt.\lt/span\gt\ltspan class='paper-ques-marks'\gt(6 marks)\lt/span\gt \lt/span\gt -------------- \ltspan class='paper-comments'\gt ### Choose the correct answer for the following :- \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt3 (a) (i)\lt/b\gt Which of the following factor affects the Q-point stability? \ltbr\gt (A) I\ltsub\gtco\lt/sub\gt \ltbr\gt (B) coupling capacitor \ltbr\gt (C) emitter resistor \ltbr\gt (D) bypass capacitor\lt/span\gt\ltspan class='paper-ques-marks'\gt(1 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt3 (a) (ii)\lt/b\gt The inter section of the dc load line with given base current curve is the \ltbr\gt (A) h-point \ltbr\gt (B) D-point \ltbr\gt (C) Q-point \ltbr\gt (D) none of these\lt/span\gt\ltspan class='paper-ques-marks'\gt(1 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt3 (a) (iii)\lt/b\gt For an emitter follower, the voltage gain is ______ \ltbr\gt (A) unity \ltbr\gt (B) greater than unity \ltbr\gt (C) less than unity \ltbr\gt (D) zero\lt/span\gt\ltspan class='paper-ques-marks'\gt(1 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt3 (a) (iv)\lt/b\gt The best biasing stability is achieved by using _____ biasing method. \ltbr\gt (A) fixed \ltbr\gt (B) collectro to base \ltbr\gt (C) voltage divider \ltbr\gt (D) none of these\lt/span\gt\ltspan class='paper-ques-marks'\gt(1 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt3 (b)\lt/b\gt Explain the working of collector-to-base bias circuit using an NPN transistor and derive the equation for I\ltsub\gtB\lt/sub\gt.\lt/span\gt\ltspan class='paper-ques-marks'\gt(8 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt3 (c) \lt/b\gt Define stability factor and discuss the factor that cuase instability of biasing circuits.\lt/span\gt\ltspan class='paper-ques-marks'\gt(8 marks)\lt/span\gt \lt/span\gt -------------- \ltspan class='paper-comments'\gt ### Choose the correct answer for the following :- \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt4 (a) (i)\lt/b\gt FET is a _____ controlled device.\ltbr\gt (A) Voltage \ltbr\gt (B) Current \ltbr\gt (C) Pulse \ltbr\gt (D) Power\lt/span\gt\ltspan class='paper-ques-marks'\gt(1 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt4 (a) (ii)\lt/b\gt PNPN device is an _____ \ltbr\gt (A) UJT \ltbr\gt (B) SCR \ltbr\gt (C) MOSFET \ltbr\gt (D) MODFET \lt/span\gt\ltspan class='paper-ques-marks'\gt(1 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt4 (a) (iii)\lt/b\gt _____ used as a relaxation oscillator. \ltbr\gt (A) MOSFET \ltbr\gt (B) SCR \ltbr\gt (C) BJT \ltbr\gt (D) UJT\lt/span\gt\ltspan class='paper-ques-marks'\gt(1 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt4 (a) (iv)\lt/b\gt The intrinsic standoff ratio of UJT _____ \ltbr\gt (A) eqaul to one \ltbr\gt (B) must be less than unity \ltbr\gt (C) must be greater than unity \ltbr\gt (D) must be zero\lt/span\gt\ltspan class='paper-ques-marks'\gt(1 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt4 (b)\lt/b\gt Explain the working of two transistor model of an SCR and obtain the expression for the anode current.\lt/span\gt\ltspan class='paper-ques-marks'\gt(8 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt4 (c) \lt/b\gt Draw the equivalent circuit and VI-characteristics of UJT and explain it.\lt/span\gt\ltspan class='paper-ques-marks'\gt(8 marks)\lt/span\gt \lt/span\gt -------------- \ltspan class='paper-comments'\gt ### Choose the correct answer for the following :- \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt5 (a) (i)\lt/b\gt Oscillaor uses ______ type of feedback. \ltbr\gt (A) positive \ltbr\gt (B) negative \ltbr\gt (C) reverse \ltbr\gt (D) both A and B\lt/span\gt\ltspan class='paper-ques-marks'\gt(1 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt5 (a) (ii)\lt/b\gt The frequency of osclillators in an oscillator is given by _____ \ltbr\gt $$ (A) \ \dfrac {1}{2\pi LC}\$$B) \ 2\pi LC \$$C) \ 2\pi\sqrt{LC}\$$D) \dfrac {1}{2\pi \sqrt{LC}}\$$
(1 marks)
5 (a) (iii) With negative feedback, the bandwidth of an amplifier _____
(A) decreases
(B) increases
(C) both A and B
(D) constant
(1 marks)
5 (a) (iv) ______ times maximum voltage gain.
(A) 0.707
(B) 7.07
(C) 10
(D) 17.06
(1 marks)
5 (b) Draw the frequency repsonse of an RC-coupled amplifier and explain it. Mention its advantages and disadvantages.(8 marks) 5 (c) Explain with the help of circuit diagram the working of an RC phase shift oscillator using transistor.(6 marks) 5 (d) In a transistor colpitts oscillator having tank circuit parameters as c<sib>1=0.001 ?F and c2=0.01 ?F if L=5?H, calculate the frequency of oscillations.</sib>(2 marks)


Choose the corect answer for the following :-

6 (a) (i) The gain of the voltage follower is ______
(A) zero
(B) infinity
(C) neagative
(D) unity
(1 marks)
6 (a) (ii) Ideally open loop gain of op-amp is _____
(A) 0
(B) 1
(C) ?
(D) positive
(1 marks)
6 (a) (iii) The CMRR is given by _____
(A) Ad × Ac
(B) Ac / Ad
(C) Ad / Ac
(D) none of these
(1 marks)
6 (a) (iv) Maximum rate of charge of output voltage with time is called _____
(A) CMRR
(B) Slew rate
(C) over rate
(D) none of these
(1 marks)
6 (b) List the characteristics of an ideal-op-amp and draw the three input inverting summer circuit using an op-amp and derive an expression for output voltage.(8 marks) 6 (c) Draw the basic block diagram of a cathode ray tube and explain its working.(8 marks)


Choose the correct answer for the following :-

7 (a) (i) Two's compliant of (1001)2 is _____
(A) 1001
(B) 0010
(C) 0111
(D) 1010
(1 marks)
7 (a) (ii) To represent 35 in binary, number of bits required is _____
(A) 6
(B) 5
(C) 4
(D) 33
(1 marks)
7 (a) (iii) Decimal number 37 is represented in BCD by _____
(A) 100111
(B) 00111011
(C) 00110111
(D) 111100
(1 marks)
7 (a) (iv) Over modulation exists when modulation index is _____
(A) 1
(B) 0
(C) >1
(D) <1
(1 marks)
7 (b) Explain the need for modulation.(6 marks) 7 (c) Convert (A3B)16=( )10 and (247.75)10= ( )2.(4 marks) 7 (d) (i) Perform (FC02A)16-(D052)16 using 16's complement.
(ii) Subtract (4317.46)8 from (42.345)8 using 8's complement.
(6 marks)


Choose the correct answer for the following :-

8 (a) (i) The expression for half adder carry with input A and B given by _____
(A) A+B
(B) AB
(C) A B
(D) none of these
(1 marks)
8 (a) (ii) The complement of A+B+1 is _____
(A) 0
(B) A+1
(C) AB+1
(D) 1
(1 marks)
8 (a) (iii) ABCD+ABD is equal to _____
(A) ABC
(B) ABC
(C) ABD
(D) ABD
(1 marks)
8 (a) (iv) A+(B+C)=(A+B)+C is _____ law.
(A) associative
(B) commutative
(C) distributive
(D) none of these
(1 marks)
8 (b) Design a full adder circuit and realize, using two half adders.(8 marks) 8 (c) Simplify the following expression and implement using only NAND gates :
$$ (i)\ Y=ABC+A\bar{B}C+AB\bar{C}+\bar{A}BC\$$ii) \ Y=\overline{\overline{AB}+\overline {AC}} \$$iii) \ Y=A+\bar{A}B $$
(8 marks)

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