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## Download Question Paper of "Digital Electronics 2 BSC IT(D)" , Question Paper of BSC IT(D) 2nd Semester, Subject Code : DCA-201, Paper ID A0305, Paper 3

• Wednesday, June 29, 2016
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Roll No. ...........................
Total No. of Questions : 13]

# DIGITAL ELECTRONICS

Time : 03 Hours

# Instruction to Candidates:

1)             Section - A is  Compulsory.
2)             Attempt any Nine questions from Section -  B.

# Section - A

 a) (15 × 2 = 30) Why should one study octal & Hexadecimal systems  when the digital machine understands only binary  system? b) Simplify the Boolean equation (A +  AB). c) Where do we use signed binary  number? d) Convert decimal 1000 to octal and Hexadecimal  system. e) What is the utility of floating point representation of  numbers? f) Write the  truth table of 2-input Ex-NOR  gate. g) How NOT gate function can be obtained from NOR   gate? h) Explain where do we use  MUX? i) What is the function of an  Encoder? j) Define with example, a combinational circuit. k) Draw a labelled block diagram of a -ve edge triggered J-K Flip  Flop. l) Explain difference between volatile and Non-volatile memories. m) Explain what do you mean by secondary   memories. n) What are the applications of D-Flip Flop? o) Where do we use DC PRESET and DC CLEAR terminals in Flip Flops?
Section - B
(9 × 5 = 45)
Q2)    If  A  =  1001 and  B  =  1100 (Both in  binary) find A+B  and   A–B ( by           2’s complement  method)

Q3)    Convert

(a)   Decimal 200.154 to binary octal and hexadecimal  systems.
(b)   Hexadecimal FF to octal.

Q4)    Express the Boolean function F = xy +  x¢z in a product of maxterm form.

Q5)    Given the following Boolean  function:

F = A¢C + A¢B + A. B¢ C + BC

(a)      Express it in sum of minterm.

(b)     Find the minimal sum of products  expression.

Q6) Simplify the following Boolean function F together with the don’t care conditions d; then express the simplified function in sum of  minterms.
f(x, y, z)  =  å   (0, 1, 2, 4, 5)

d(x, y, z)  =  å   (3, 6, 7)
Q7)    Write the truth table of Half-subtractor and from it realize its circuit.

Q8)  Write the truth table of a Full Adder and then derive its circuit in terms  of half adders.
Q9)    Draw the circuit of 3 to 8 decoder and explain  it.
Q10) (a)  Draw the symbols of the various logic gates you have                       studied.
(b) Explain how a demultiplexer ( 1 to 8) function can be obtained         from a 3 to 8 decoder.
Q11) Derive the circuit of an edge triggered J-K Flip Flop from the basic S-R Flip Flop. Discuss its truth table. How race around problem can be solved in a J-K Flip Flop?
Q12) Discuss:
(a)      Classification of memories.
(b)     Advantages of semiconductor memories.
(c)      Explain the difference between static and dynamic memories.
Q13) Draw the circuit of an S-R Flip Flop using NOR gates . Write its truth table and explain why there is a forbidden state. Is there any racing, if so explain it?