DipIETE – ET (OLD SCHEME)

 

Flowchart: Alternate Process: JUNE 2010Code: DE09                                                                          Subject: DIGITAL ELECTRONICS

Time: 3 Hours                                                                                                     Max. Marks: 100

 

 

NOTE: There are 9 Questions in all.

·      Question 1 is compulsory and carries 20 marks. Answer to Q.1 must be written in the space provided for it in the answer book supplied and nowhere else.

·      Out of the remaining EIGHT Questions, answer any FIVE Questions. Each question carries 16 marks.

·      Any required data not explicitly given, may be suitably assumed and stated.

 

 

Q.1       Choose the correct or the best alternative in the following:                                  (210)

                                

a.       The decimal equivalent of Hex number 1A53 is __________.

 

                   (A)  6793                                            (B)  6739

(C)    6973                                           (D)  6379

       

b.      The simplification of the Boolean expression  +  is _________.

 

(A)    0                                                  (B)  1

(C)  A                                                 (D)  BC

            

             c.   De Morgan’s first theorem shows the equivalence of

                    

(A)    NOR Gate and AND Gate.

(B)    NAND Gate and AND Gate.

(C)  NOR Gate and Bubbled AND Gate.

(D)  NAND Gate and Bubbled.

 

             d.   The fastest of all logic families is __________.

 

                   (A)  TTL                                             (B)  ECL

(C)  CMOS                                        (D)  RTL

 

             e.   A Ring Counter consists of Five Flip-Flops will have __________.  

                  

(A)     32 states                                      (B)   5 states

(C)  16 states                                      (D)  10 states

 

             f.    The gates required to build a Half-adder logic circuit are _________.

 

(A)     EX-OR Gate and OR Gate

(B)     OR Gate and AND Gate

(C)  EX-OR Gate and AND Gate

(D)  EX-OR Gate and EX-OR Gate

 

             g.   If the input to a T Flip-Flop is 100 Hz signal, then the final output of the three T Flip-Flops in cascade is _________.

 

(A)  100 Hz                                         (B)  22.5 Hz

(C)  50 Hz                                           (D)  12.5 Hz

 

 

             h.   EPROM contents can be erased by exposing it to __________.

 

(A)    ultraviolet rays                              (B)  infrared rays

(C)  burst of microwaves                     (D)              intense heat radiations

 

             i.    The A/D converter which has maximum speed of conversion is _________.

 

(A)   Successive Approximation            (B) Parallel Comparator

(C) Dual Slop                                      (D) Counting Type

 

             j.    A device which converts BCD to Seven Segment is called

 

(A)  Multiplexer.                                  (B)  Encoder.

(C)  Decoder.                                      (D)  Demultiplexer.

 

 

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

 

 

  Q.2     a.   (i)    Convert the Decimal number 82.67 to its Binary Equivalent.                        (3)

                   (ii)   Convert the binary equivalent of decimal number 82.67 into

                           Hexadecimal.                                                                                             (3)

         (iii)  Convert the binary equivalent of decimal number 82.67 into Octal                        number.                                                          (3)

                                                                                                                                                

             b.   (i)    Perform the Addition of 20 and (–15) using 2’s Complement.                     (4)

                    (ii)   Convert the Decimal number 430 to Excess-3 code.                                   (3)

                                                                                                                                                                       

  Q.3     a.   What are universal gates? Realize the AND and OR gates using NAND gate.                     (6)

                 

c.       Prove the following equations using Boolean Algebraic Theorems:                   (4+6)

(i)

(ii)                                                    

                    

  Q.4     a.   Minimize the logic function F(A, B, C, D) = ∑ m(1,3,5,8,9,11,15) + d(2,13) using K-maps and realize the simplified logic function  using NAND gates only.                                                               (9)

 

             b.   What are the advantages of CMOS Logic? Explain the operation of CMOS Inverter with the help of logic diagram.                                              (7)

 

  Q.5     a.   What is a Full-adder? Explain a full-adder with the help of truth-table and logic diagram.                 (9)       

                                                                                                                                                                                   

             b.   What is an Encoder? Explain Decimal to BCD Encoder with the help of truth-table and logic diagram.                                                                    (7)

 

  Q.6     a.   What is a Shift Register? What are its various types? List out their applications.                   (4)

       

             b.   What are Synchronous Counters? Design a MOD-5 Synchronous counter using J-K Flip-Flops.                                                                (12)

                                                                                                                        

  Q.7     a.   Differentiate between ROM, PROM, EPROM, UV EPROM, EEPROM.          (6)   

                                                                                                                        

             b.   Using a suitable logic diagram explain the operation of 16-bit ROM Array.        (10)

 

  Q.8     a.   With the help of R-2R binary ladder, explain the working of a 4-bit D/A converter.            (12)

 

             b.   A 6 bit R-2R ladder D/A converter has a reference voltage of 5 V. It meets standard linearity.  Find:

                   (i)  The resolution in percent and

                   (ii) The output voltage for 011100.                                                                     (4)

 

  Q.9     a.   Design a 4 to 1 Multiplexer by using the three variable function given by

                                         F(A,B,C)=∑m(1,3,5,6)                                                               (9)                                                                                                                                                                                                                                                                                                                   

                                                                

b.   What is a Flip-Flop? Mention its various applications.                                         (3)

 

      c.  Find the conversion time of a successive approximation A/D converter              which uses a 2 MHz clock and a 5 bit binary ladder containing 8 V            reference. Also find out its conversion Rate.           (4)                                                                                                                                                                        .                                                          (8)