MODEL QUESTION PAPER
FIRST SEMESTER
SUBJECT : DIGITAL ELECTRONICS-1
Common to E&C ,EI&C,CS&E and IS&E.
SUBJECT: DIGITAL ELECTRONICS-I
TIME :3 HRS MAX.MARKS :100
Note: 1)Section A is compulsory.
2) Answer any two main questions from each of the remaining Sections
SECTION: A
1 a. Fill in the blanks with suitable words 5X1
(i) The radix of hexadecimal number system is _______________
(ii) The number of flip-flops required for decade counter is ______________
(iii) Race around condition is eleminated in ________________ flip flop
(iv) An example for unsaturated logic _________ Ics
(v) The SISO shift register with feed back _________ counter
b. Write a note interfacing between TTL and CMOS Ics 5
SECTION: B
2 a. Define the radix of a number system 2
b. Convert the following from Binary to Decimal number system 8
(i) 11001001 (ii) 1110.1111
(iii) 11001111 -->( )h (iv) 1AF--> ( ) D
c. Subtract the following using 2's complemnet method
(i) 1FE2- 0AC2 (ii) 412.6 - 255.0 5
3 a. Convert the following gray code to binary code (i) 110101 (ii) 111110 2
b. Convert the following Excess-3 code to binary code (i) 11011 (ii) 10110 3
c. Differentiate analog and digital signals 5
d. Expalin AND logic with symbol, logic expression and truth table, . 5
4 a. Define Noise Margin and power dissipation with reference to logic families 4
b. State Associative and Distributive laws of Boolean Algebra 4
c. Simplfy the following expressions and realize the same using gates
(i) A+(BC.(D+E)+ B)) (ii) (A+B).(C+D).(AB+CD) 7
SECTION: C
5 a. What is a Full adder? Use K- map to derive logic expressions for its output 7
b . Compare serial and parallel adders 3
c . Explain the operation of 4-bit parallel adder 5
6 a . What is a priority encoder? 2
b. Write the logic circuit and truth table of Decimal to BCD encoder 8
c. Write the logic circuit and truth table of BCD to seven segment decoder for common
anode display 5
7 a. What is a multiplexer? 2
b Explain the 8:1 multiplexer with the help truth table and logic circuit 6
c . What is the use of De-multiplexer? Write the truth table and logic circuit of
4:1 De-multiplexer 7
SECTION: D
8 a. Differentiate between combinational and seqential circuits 3
b . Explain the operation of clocked RS-FF using NAND gates 6
c. What is meant by Race around condition? How it is overcome? 7
9 a . Explain the logic diagram, truth table and timing diagram,
the operation of 4-bit ripple counter 8
b. What do you by modulus of counter? 2
c . Explain how decoding gates can be used for construction of mod-11 counter 5
10 a . Explain with logic diagram, truth table and timing diagram,
the operation of a 4-bit shift counter 8
b. Write the logic diagram of a 4-bit shift register.
Write the truth table and timing diagram for a 4-bit SISO register for a data of 1011 ( 7 )
