##### B.Sc. Hons. Electronics 2011 questions View the solutions
###### Digital Electronics: 30

1.(a)Subtract (l1101.01)_{2} from (11110.11)_{2}. 2
(b)Show that bar(bar(bar(AB).A).bar(bar(A.B).B))= bar(A.B)+bar(A).B 3
(c)Find the l0’s complement of 156 using BCD notation. 3
(d)Explain the propagation delay of a digital circuit. 2

2. (a) Draw the circuit diagram of 2-input NAND gate using bipolar transistors only. Define Fan-out for a digital logic gate. 2+l
(b) Express F(A,B,C) = AC + A.bar(B) ncanonical sum-of-product (SOP) terms. 3
(c) Using Karnaugh mapping technique find out the reduced SOP and POS form for the function F =Summation { m(1,2,3,5,6,7) }. 4

3. (a) Write down the truth table for a 4:1 MUX with high enable input. Design such a MUX using AND-OR logic and explain its operation. 2+4
b) Show with a suitable circuit diagram that the functions F(X,Y)=X+Y and F(X,Y)=bar(X+Y) can be implemented by using a 2:l MUX. 2+2

4.(a) Give the truth table of a J-K Flip-flop. What is race around condition in such a flip flop? Explain with a suitable diagram how race around condition is eliminated. 1+2+5
(b) How the J-K flip-flop can be used as a D-flip-flop? 2

5. (a) What is the need of an ADC ? Give the block diagram of a successive approximation type ADC ard explain its operation. 1+6
(b) What are EPROM and EEFROM ? Mention the methods of erasing these two. 2+1

###### Microprocessor : 20

6.(a) What are the functions of the ALU and timing and control unit of a microprocessor? 4
(b)What are the instruction cycles in 8085 microprocessor? Explain fetch cycles and execution cycle of an instruction with proper timing diagram. 2+4

7.(a) What is a BUS in a microprocessor? What are address bus and address/data BUS in case of a 8O85 microprocessor? 1+4
b) What are the functions of the program counler and stack pointer in case of a microprocessor? What are the instructions used in stack operation? 4+1

8. (a) What is meant by input/output (I/O) devices? Name the control signals by which microprocessor differentiates between an input and an output device. 1+2
(b) Name and describe the operation of different interrupt signals used in 8085. 4
(c) Explain the function of a DMA. 3

###### Communication : 30

9.(a)What is meant by channel bandwidth? 2
(b)Distinguish the following systems: 2+2
(i)Time invariant and time varying systems.
(ii)Energy and power signals.
(c)Verify Parseval's theorem for the signal e^{-at} u(t) for a>0. 4

10.(a)Draw the specta of SSB and VSB. 2
(b)A carrier signal of frequency 5 MHz ard peak value 5V is amplitude modulated by a 4 KHz sine-wave of amplitude 3V. Determine the modulation index, the upper sideband and lower sideband frequencies, and their amplitudes. 4
(c) Explain with the help of a suitable circuit diagram the operation of a square-law modulator for generating the amplitude modulated(AM) signal. 4

11. (a) Define frequency deviation in a frequency modulation process. What is its impact on transmission bandwidth? 2
(b) Is it possible to generate a phase modulated signal from a frequency modulated signal? Justify your answer. 3
(c) Consider an angle modulated signal x(t) = 2cos [2pi10^{5}t + 3sin(2pi10^{2}t] and find (a) its instantaneous frequency at time t = 0.4ms and (b) maximum phase deviation and frequency deviation. 3
(d) Comment with reasons the statement : FM is superior to AM. 2

12. (a) Write down the need for sampling a signal. What is Nyquist criteria for a sampling process? calculate the sampling interval and minimum sampling rate for the signal m(t) = 10cos(2000pi t)cos(8000pi t). 2+1+3
(b) Define the following modulation processes by the help of relevant diagrams: (i) PWM; (ii) PPM. 2+2

13. (a) Give the structure of the atmosphere, both at day and night. 4
(b) What are meant by maximum usable frequency in connection with radiowave propagation ? 4
(c) Define noise figure and noise temperature. 2

###### Computer Science : 20

14. (a) Draw the diagram of basic buiiding blocks of a computer and briefly describe the operation of each block. 2+6
b) What is the role of compiler in executing a computer program ? 2
15. (a) What is a link list ? Explain the important features of a linked data-structure. 1+2
(b) Compare and contrast the basic features of Windows XP and a Linux system. 5
(c) What is an assembler and what is its primary function ? 2

16. (a) What is meant by topologies in a Local Area Network (LAN) system ? Explain with suitable diagam the following LAN topologies :
(i) Star;
(ii) Mesh;and
(iii) Ring. 8
(b) What are the needs of a hub and a router ? 2