Previous year question paper for DE1 (Diploma Electronics and Communication Engineering 3rd)

1. Introduction

a) Define digital and analog signals and systems, difference between analog and

digital signals

b) Need of digitization and applications of digital systems

(02 hrs)

2. Number Systems

a) Decimal, binary, octal, hexadecimal number systems

b) Conversion of number from one number system to another including decimal

points

c) Binary addition, subtraction, multiplication,1’s and 2’s complement method of

subtraction

d) BCD code numbers and their limitations, addition of BCD coded numbers,

conversion of BCD to decimal and vice-versa

e) Excess-3 code, gray code, binary to gray and gray to binary conversion

f) Concept of parity, single and double parity, error detection and correction using

parity

(10 hrs)

3. Logic Gates

a) Logic gates, positive and negative logic, pulse waveform, definition, symbols,

truth tables, pulsed operation of NOT, OR, AND, NAND, NOR, EX-OR, EX-NOR

gates

b) NAND and NOR as universal logic gates

(04 hrs)

81

4. Logic Simplification

a) Rules and laws of Boolean algebra, logic expression, Demorgan’s theorems,

their proof

b) Sum of products form (minterm), Product of sum form (MAXTERMS), simplification of Boolean expressions with the help of Rules and laws of Boolean

algebra

c) Karnaugh mapping techniques upto 4 variables and their applications for

simplification of Boolean expression

(08 hrs)

5. Arithmetic Circuits

a) Half adder, full adder circuits and their operation

b) Parallel binary adder, 2-bit and 4-bit binary full adder, block diagram, working

(03 hrs)

6. Multiplexer/Demultiplexer

a) Basic functions, symbols and logic diagrams of 4-inputs and 8-inputs

multiplexers,

b) Function/utility of 16 and 32 inputs multiplexers,

c) Basic function, symbols and logic diagram of 4 outputs and 8 output DEMUX

d) Realization of Boolean expression using multiplexer/demultiplexers

(04 hrs)

7. Decoders, Display Devices and Associated Circuits

a) Basic Binary decoder, 4-line to 16 line decoder circuit

b) BCD to decimal decoder, BCD to 7-segment decoder/driver, LED/LCD display

(04 hrs)

8. Encoders and Comparators

a) Encoder, decimal to BCD encoder, decimal to BCD priority encoder, keyboard

encoder

b) Magnitude comparators, symbols and logic diagrams of 2-bit and 4-bit

comparators

(04 hrs)

9. Latches and Flip-Flops

a) Latch, SR-latch, D-latch, Flip-flop, difference between latch and flip-flop

(07 hrs)

82

b) S-R, D flip-flop their operation using waveform and truth tables, race around

condition

c) JK flip-flop, master slave and their operation using waveform and truth tables

10. Counters

a) Asynchronous counter, 4-bit Asynchronous counter, Asynchronous decade

counter

b) Synchronous counter, 4-bit synchronous binary counter. c) Up/down Asynchronous counters 3 bit Asynchronous up/down counter.

d) Ring counter, cascaded counter, counter applications

(10 hrs)

11. Shift Registers

a) Shift registers functions, serial-in-serial out, serial-in-parallel-out, parallel-in- serial-out, parallel-in-parallel out shift register

b) Universal shift register, shift register counter and applications of shift registers