Friday, 9 December 2011

Model question paper of DIGITAL ELECTRONICS of Diploma 1st Sem - E C

            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 )

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