Basic Electronics - Jan 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) 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) (ii) The efficiency of full waves rectifier is about _____ %
(A) 40.6
(B) 0.46
(C) 1.21
(D) 81.2(1 marks) 1 (a) (iii) The missing terms in the forward diode current is I_F=I₀ [e^v/v_r-1]
(A) V_R
(B) ?
(C) V_S
(D) e(1 marks) 1 (a) (iv) The zener diode is mainly used in
(A) Comparator
(B) Regulator
(C) Multivibrator
(D) None of these(1 marks) 1 (b) Discuss the behaviour of p-n junctions under:
(i) No bias
(ii) Forward bias
(iii) Reverse bias.(6 marks) 1 (c) Explain the operation of full wave bridge rectifire with neat circuit diagram and waveforms.(6 marks) 1 (d) A zener diode has a breakdown voltage of 10V. It is supplied from a voltage source varying between 20-40V in series with resistance of 820? using an ideal zener diode model obtain minimum and maximum zener currents.(4 marks)

Choose the correct answer for the following :-

2 (a) (i) When transistor operated in cut off and saturation, it acts like
(A) a linear amplifier
(B) a switch
(C) a variable capacitor
(D) a variable resistor(1 marks) 2 (a) (ii) If the base emitter junction is open, what is the collector current.
(A) 1 mA
(B) 2 mA
(C) 10 mA
(D) 0(1 marks) 2 (a) (iii) The ______ transistor is used for impedance matching.
(A) C-B
(B) C-E
(C) C-C
(D) None of these(1 marks) 2 (a) (iv) ? of a transistor is 0.99 calculate ?
(A) ?=0.9
(B) ?=90
(C) ?=99
(D) ?=0.09(1 marks) 2 (b) Draw the cammon emitter circuit and sketch the output characteristics, explain active region cutoff region and saturation region by indicating them on the characteristics curve.(8 marks) 2 (c) With a neat diagram explain the working of transistor used as voltage amplifier.(4 marks) 2 (d) For a certain transistor, 99.6% of the carrier injected into the base cross the collector-base junction. If the leakage current is 5?A and the collectro current is 20mA, calculate:
(i) The value of ?
(ii) The emitter current.(4 marks)

Choose the correct answer for the following :-

3 (a) (i) The best biasing stability is achieved by using _____ biasing method.
(A) Fixed
(B) Collector to base
(C) Voltage divider
(D) None of these(1 marks) 3 (a) (ii) In self bias or emitter bias circuit _____ is connected between emitter and ground.
(A) Inductor
(B) Capacitor
(C) Resistor
(D) Zener diode(1 marks) 3 (a) (iii) The stability factor is given by
$$ (A) \ \dfrac {dI_{\infty}}{dI_E}\$$B) \ \dfrac {dI_B}{dI_{\infty}}\$$C) \ \dfrac {dI_E}{dI_{\infty}}\$$D) \ \dfrac {dI_C}{dI_{\infty}}\\$$\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 operating point must be _____ for the proper operation transistor \ltbr\gt (A) High \ltbr\gt (B) Stable \ltbr\gt (C) Increasing \ltbr\gt (D) Decreasing \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 With a neat circuit diagram, explain the working of an 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(6 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt3 (c) \lt/b\gt Determine the operating point for a silicon transistor biased by base bias method with &betal=100, R\ltsub\gtB\lt/sub\gt=500K?, R\ltsub\gtC\lt/sub\gt=2.5K? and V\ltsub\gtCC\lt/sub\gt=20V. Also draw the load line.\lt/span\gt\ltspan class='paper-ques-marks'\gt(6 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt3 (d)\lt/b\gt Derive the stability factor S for base bias circuit.\lt/span\gt\ltspan class='paper-ques-marks'\gt(4 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 With gate open if the supply voltage exceeds the break over voltage of SCR, then SCR will conduct \ltbr\gt (A) False \ltbr\gt (B) True \ltbr\gt (C) Only for D.C. \ltbr\gt (D) Only for A.C.\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 The SCR is a _____ device \ltbr\gt (A) NPN \ltbr\gt (B) PNP \ltbr\gt (C) PNPN \ltbr\gt (D) PNN\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 A relaxation oscillator uses _____ \ltbr\gt (A) MOSFET \ltbr\gt (B) SCR \ltbr\gt (C) UJT \ltbr\gt (D) BJT\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 FET is a _____ controlled device \ltbr\gt (A) Voltage \ltbr\gt (B) Current \ltbr\gt (C) Power \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\gt4 (b)\lt/b\gt Explain the construction of n-channel JFET and give its symbol.\lt/span\gt\ltspan class='paper-ques-marks'\gt(6 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt4 (c) \lt/b\gt Write and explain the equivalent circuit of UJT.\lt/span\gt\ltspan class='paper-ques-marks'\gt(5 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt4 (d)\lt/b\gt Explain the two transistor model of SCR.\lt/span\gt\ltspan class='paper-ques-marks'\gt(5 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 Oscillator uses _____ type of feedback \ltbr\gt (A) Positive \ltbr\gt (B) Negative \ltbr\gt (C) Reverse \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\gt5 (a) (ii)\lt/b\gt The total phase shift around a loop must be _____ for the sutained oscillations. \ltbr\gt (A) 180° \ltbr\gt (B) 360° \ltbr\gt (C) 90° \ltbr\gt (D) 270°\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) (iii)\lt/b\gt The frequency response is a graph of _____ \ltbr\gt (A) frequency V\ltsub\gts\lt/sub\gt current gain \ltbr\gt (B) frequency V\ltsub\gts\lt/sub\gt voltage gain \ltbr\gt (C) frequency V\ltsub\gts\lt/sub\gt output voltage \ltbr\gt (D) frequency V\ltsub\gts\lt/sub\gt input voltage\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) (iv)\lt/b\gt In RC coupled amplifier the d.c. component is blocked by _____ \ltbr\gt (A) Load reistance R\ltsub\gtL\lt/sub\gt. \ltbr\gt (B) Coupling capacitor, C\ltsub\gtc\lt/sub\gt \ltbr\gt (C) R\ltsub\gtB\lt/sub\gt \ltbr\gt (D) The transistor\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 (b)\lt/b\gt With a neat circuit diagram, explain the working of a two stage capacitor coupled CE amplifier.\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\gt5 (c) \lt/b\gt Explain with the help of circuit diagram the working of an RC phase shift oscillator using transistor.\lt/span\gt\ltspan class='paper-ques-marks'\gt(6 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt5 (d) \lt/b\gt Find the frequency of the oscillator of transistorized Colpitts oscillator having tank circuit parameters as C\ltsub\gt1\lt/sub\gt=15pF, C\ltsub\gt2\lt/sub\gt=1.5nF and L=50?H.\lt/span\gt\ltspan class='paper-ques-marks'\gt(2 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt6 (a) (i)\lt/b\gt In an inverting amplifier there is _____ phase shift between input and output. \ltbr\gt (A) 0° \ltbr\gt (B) 90° \ltbr\gt (C) 180° \ltbr\gt (D) 360°\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\gt6 (a) (ii)\lt/b\gt Ideally open loop gain of op-amp is _____ \ltbr\gt (A) 0 \ltbr\gt (B) 1 \ltbr\gt (C) ? \ltbr\gt (D) Negative\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\gt6 (a) (iii)\lt/b\gt When op-amp used as integrator with inputs as sqaure wave the output will be \ltbr\gt (A) Rampn \ltbr\gt (B) Triangular wave \ltbr\gt (C) Cosine wave \ltbr\gt (D) Step\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\gt6 (a) (iv)\lt/b\gt Lissajous figure are used to measure _____ differece between sinusoidal signals \ltbr\gt (A) Phase \ltbr\gt (B) Amplitude \ltbr\gt (C) Frequency \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\gt6 (b)\lt/b\gt Write the ideal op-amp characteristics.\lt/span\gt\ltspan class='paper-ques-marks'\gt(6 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt6 (c) \lt/b\gt Show with a circuit diagram how an op-amp can be used as differentiator.\lt/span\gt\ltspan class='paper-ques-marks'\gt(6 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt6 (d)\lt/b\gt Explain how current measurement is done using CRO.\lt/span\gt\ltspan class='paper-ques-marks'\gt(4 marks)\lt/span\gt \lt/span\gt -------------- \ltspan class='paper-comments'\gt ### Choose the correct answe for the following :- \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt7 (a) (i) \lt/b\gt Which of the following is invalid BCD code? \ltbr\gt (A) 0011 \ltbr\gt (B) 1101 \ltbr\gt (C) 0101 \ltbr\gt (D) 1001\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\gt7 (a) (ii)\lt/b\gt Given the number (8BF)\ltsub\gt16\lt/sub\gt what is the positional weight of the 8? \ltbr\gt (A) 16 \ltbr\gt (B) 256 \ltbr\gt ? 4096 \ltbr\gt (D) 8192\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\gt7 (a) (iii)\lt/b\gt (64)\ltsub\gt16\lt/sub\gt-(46)\ltsub\gt8\lt/sub\gt in binary is \ltbr\gt (A) 111101101 \ltbr\gt (B) 111101100 \ltbr\gt (C) 111110 \ltbr\gt (D) 1100110\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\gt7 (a) (iv)\lt/b\gt The relation between carrier poewer and total power in an AM wave _____ \ltbr\gt $$ (A) \ P_C=P_T\left(1+\dfrac {m^2}{4} \right )\$$B) \ P_C=P_T\left(1+\dfrac {m^2}{2} \right )\$$C) \ P_T=P_C\left(1+\dfrac {m^2}{4} \right )\$$D) \ P_T=P_C\left(1+\dfrac {m^2}{2} \right )\$$(1 marks) 7 (b) Determine the value of base x, if (i) (225)_x=(341)₈; (ii) (211)_x=(152)₈(6 marks) 7 (c) Perform subtraction using 2's complement method 1101 - 1010(4 marks) 7 (d) Draw the block diagram of super heterodyne receiver and explain the functions of each block.(6 marks)

Choose the correct answer for the following :-

8 (a) (i) De Morgan's therorem states that A+B is
(A) A+ B
(B) A. B
(C) AB
(D) A +B(1 marks) 8 (a) (ii) Universal gates are ______ and ______,
(A) NOT and NOR
(B) AND and OR
(C) NAND and NOR
(D) XOR and XNOR(1 marks) 8 (a) (iii) For which gate when the two inputs A and B are equal the output is zero and otherwise one?
(A) NAND
(B) NOR
(C) EXNOR
(D) EXOR(1 marks) 8 (a) (iv) An half adder has two inputs and _____ outputs
(A) ONE
(B) TWO
(C) THREE
(D) None of these(1 marks) 8 (b) Implement EX-NOR gate using only NOR gates. (4 marks) 8 (c) Simplify AB+ AC+A BC(AB+C).(6 marks) 8 (d) Implement full adder using two half adders and one OR gate. Write the equations for sum and C_out.(6 marks)