VTU First Year Engineering (C Cycle) (Semester 1)
Basic Electronics
December 2013
Total marks: --
Total time: --
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

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 M
1 (a) (ii) The efficiency of full waves rectifier is about _____ %
(A) 40.6
(B) 0.46
(C) 1.21
(D) 81.2
1 M
1 (a) (iii) The missing terms in the forward diode current is IF=I0 [ev/vr-1]
(A) VR
(B) ?
(C) VS
(D) e
1 M
1 (a) (iv) The zener diode is mainly used in
(A) Comparator
(B) Regulator
(C) Multivibrator
(D) None of these
1 M
1 (b) Discuss the behaviour of p-n junctions under:
(i) No bias
(ii) Forward bias
(iii) Reverse bias.
6 M
1 (c) Explain the operation of full wave bridge rectifire with neat circuit diagram and waveforms.
6 M
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 M

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 M
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 M
2 (a) (iii) The ______ transistor is used for impedance matching.
(A) C-B
(B) C-E
(C) C-C
(D) None of these
1 M
2 (a) (iv) ? of a transistor is 0.99 calculate ?
(A) ?=0.9
(B) ?=90
(C) ?=99
(D) ?=0.09
1 M
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 M
2 (c) With a neat diagram explain the working of transistor used as voltage amplifier.
4 M
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 M

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 M
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 M
3 (a) (iii) The stability factor is given by
\[ (A) \ \dfrac {dI_{\infty}}{dI_E}\\(B) \ \dfrac {dI_B}{dI_{\infty}}\\(C) \ \dfrac {dI_E}{dI_{\infty}}\\(D) \ \dfrac {dI_C}{dI_{\infty}}\\\]
1 M
3 (a) (iv) The operating point must be _____ for the proper operation transistor
(A) High
(B) Stable
(C) Increasing
(D) Decreasing
1 M
3 (b) With a neat circuit diagram, explain the working of an collector-to-base bias circuit using an npn transistor and derive the equation for IB.
6 M
3 (c) Determine the operating point for a silicon transistor biased by base bias method with &betal=100, RB=500K?, RC=2.5K? and VCC=20V. Also draw the load line.
6 M
3 (d) Derive the stability factor S for base bias circuit.
4 M

Choose the correct answer for the following :-
4 (a) (i) With gate open if the supply voltage exceeds the break over voltage of SCR, then SCR will conduct
(A) False
(B) True
(C) Only for D.C.
(D) Only for A.C.
1 M
4 (a) (ii) The SCR is a _____ device
1 M
4 (a) (iii) A relaxation oscillator uses _____
1 M
4 (a) (iv) FET is a _____ controlled device
(A) Voltage
(B) Current
(C) Power
(D) None of these
1 M
4 (b) Explain the construction of n-channel JFET and give its symbol.
6 M
4 (c) Write and explain the equivalent circuit of UJT.
5 M
4 (d) Explain the two transistor model of SCR.
5 M

Choose the correct answer for the following :-
5 (a) (i) Oscillator uses _____ type of feedback
(A) Positive
(B) Negative
(C) Reverse
(D) None of these
1 M
5 (a) (ii) The total phase shift around a loop must be _____ for the sutained oscillations.
(A) 180°
(B) 360°
(C) 90°
(D) 270°
1 M
5 (a) (iii) The frequency response is a graph of _____
(A) frequency Vs current gain
(B) frequency Vs voltage gain
(C) frequency Vs output voltage
(D) frequency Vs input voltage
1 M
5 (a) (iv) In RC coupled amplifier the d.c. component is blocked by _____
(A) Load reistance RL.
(B) Coupling capacitor, Cc
(C) RB
(D) The transistor
1 M
5 (b) With a neat circuit diagram, explain the working of a two stage capacitor coupled CE amplifier.
8 M
5 (c) Explain with the help of circuit diagram the working of an RC phase shift oscillator using transistor.
6 M
5 (d) Find the frequency of the oscillator of transistorized Colpitts oscillator having tank circuit parameters as C1=15pF, C2=1.5nF and L=50?H.
2 M

6 (a) (i) In an inverting amplifier there is _____ phase shift between input and output.
(A) 0°
(B) 90°
(C) 180°
(D) 360°
1 M
6 (a) (ii) Ideally open loop gain of op-amp is _____
(A) 0
(B) 1
(C) ?
(D) Negative
1 M
6 (a) (iii) When op-amp used as integrator with inputs as sqaure wave the output will be
(A) Rampn
(B) Triangular wave
(C) Cosine wave
(D) Step
1 M
6 (a) (iv) Lissajous figure are used to measure _____ differece between sinusoidal signals
(A) Phase
(B) Amplitude
(C) Frequency
(D) None of these
1 M
6 (b) Write the ideal op-amp characteristics.
6 M
6 (c) Show with a circuit diagram how an op-amp can be used as differentiator.
6 M
6 (d) Explain how current measurement is done using CRO.
4 M

Choose the correct answe for the following :-
7 (a) (i) Which of the following is invalid BCD code?
(A) 0011
(B) 1101
(C) 0101
(D) 1001
1 M
7 (a) (ii) Given the number (8BF)16 what is the positional weight of the 8?
(A) 16
(B) 256
? 4096
(D) 8192
1 M
7 (a) (iii) (64)16-(46)8 in binary is
(A) 111101101
(B) 111101100
(C) 111110
(D) 1100110
1 M
7 (a) (iv) The relation between carrier poewer and total power in an AM wave _____
\[ (A) \ P_C=P_T\left(1+\dfrac {m^2}{4} \right )\\(B) \ P_C=P_T\left(1+\dfrac {m^2}{2} \right )\\(C) \ P_T=P_C\left(1+\dfrac {m^2}{4} \right )\\(D) \ P_T=P_C\left(1+\dfrac {m^2}{2} \right )\\\]
1 M
7 (b) Determine the value of base x, if (i) (225)x=(341)8; (ii) (211)x=(152)8
6 M
7 (c) Perform subtraction using 2's complement method 1101 - 1010
4 M
7 (d) Draw the block diagram of super heterodyne receiver and explain the functions of each block.
6 M

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

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