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Fourth Semester [B.Tech]  May 2005
Paper Code : ETEC – 206 Subject : Digital Circuits and Systems 
Time : 3 Hours 
Maximum Marks : 75 
Note : Attempt any 5 questions in all. 
Q1 
( a ) 
Simplify the following Boolean function: z = ( (A+B)' + B' )' 
5 
( b ) 
Explain DeMorgan's laws. 
5 

( c ) 
Show the logic diagram of boolean function of Q.1 a using NAND
gates. 
5 
Q2 
( a ) 
Give one word answer to the following:

5 
( b ) 
Design a 2 to 4 decoder using NAND gates. 
5 

( c ) 
Compare digital signals with Analog signals, clearly stating their merits and demerits. 
5 
Q3 
( a ) 
What is the simplified boolean equation for the Karnaugh map of the
figure given below:

5 

( b ) 
Draw the equivalent logic circuit of the simplified equation. 
5 

( c ) 
Implement a 4 to 16 decoder using ROM. 
5 
Q4 
( a ) 
Justify the following statements:

10 
( b ) 
Explain the functioning of Mod8 ripple counter. 
5 
Q5 
( a ) 
Differentiate between:

5x3 
Q6 
( a ) 
Find the dual of hte followin gexpressions 
3 
( b ) 
What is the cannonical form of logic expression? Explain minterms and maxterms. 
4 

( c ) 
What is a mod5 counter. How it is designed. How a decade counter can be realized using mod5 counter. 
8 
Q7 
( a ) 
Explain the function of a multiplexer. Give an example of multiplexer IC. 
5 
( b ) 
What is the difference betweeen nbit register and nbit latch. 
4 

( c ) 
What is a flipflop. Explain how an SR flip flopis realized by
employing: (i) NOR gates (ii) NOR gates 
6 
Q7 
Write short notes on any three of the following: 
5 x 3 

( a ) 
Memory organization 


( b ) 
Content Addressable Memory 


( c ) 
Code convertors 


( d ) 
Comparators 
