Digital Circuits And Logic Design Question Paper of 3rd Semester CSE74 Download Previous Years Question Paper 9

Roll No.

Total No. of Questions : 09

B.Tech.  (Sem.–3)

DIGITAL CIRCUITS & LOGIC DESIGN

Subject Code : CS-205

Paper ID : [CS205]

Time : 3 Hrs.

Instruction to candidates :

1.      Section –A is Compulsory.

2.     Attempt any Four questions from section –B

3.     Attempt any Two questions from section –C

Section –A

1.       Choose the correct or best alternative in the following:

a.     8 is equal to signed binary number

                                                             i.      10001000

                                                           ii.      00001000

                                                        iii.      10000000

                                                        iv.      11000000

b.     De-Morgan’s first theorem shows the equivalence of

                                                             i.      Or gate and exclusive OR gate.

                                                           ii.      NOR gate and Bubbled AND gate

                                                        iii.      NOR gate and NAND gate.

                                                        iv.      NAND gate and NOT gate.

c.      The digital logic family which has the lowest propagation delay time is

                                                             i.      ECL.

                                                           ii.      TTL.

                                                        iii.      CMOS.

                                                        iv.      PMOS.

d.     The device which changes from serial data to parallel data is

                                                             i.      COUNTER.

                                                           ii.      MULTIPLEXER

                                                        iii.      DEMULTIPLEXER

                                                        iv.      FLIP-FLOP

e.      A device which converts BCD to seven segment is called

                                                             i.      Encoder.

                                                           ii.      Decoder

                                                        iii.      Multiplexer

                                                        iv.      Demultiplexer

f.       In successive –approximation A/D converter, offset voltage equal to ½ LSB is added to the D/A converter’s output. This is done to

                                                             i.      Improve the speed of operation.

                                                           ii.      Reduce the maximum quantization error.

                                                        iii.      Increase the number of bits at the output.

                                                        iv.      Increase the range of input voltage that can be converted.

g.       

                                                             i.      Convert 2222 in Hexadecimal number.

                                                           ii.      Subtract -27 from 68 using 2’s complements.

                                                        iii.      Divide(101110)₂ by (101)₂

Section –B

2.     State and prove De-Morgan’s theorems.

3.     Prove the following identities using Boolean algebra:

a.     (A+B)(A+AB)C +A(B+C)+ AB+ ABC= C(A+B)+ A(B+C)

b.     A(A.B) .B(A.B) =A ±B

c.      AB+ A+ AB=0

4.     A combinational circuit has 3 inputs A, B, C and output F.F is true for following input combinations

A is false, B is true

A  is false, C is true

A B C are true

a.     Write the Truth table for F. use the convention True= 1 and False =0

b.     Write the simplified expression for F in SOP from

c.      Write the simplified expression for Fin POS from

d.     Draw logic circuit using minimum number of 2 – input NAND gates.

5.     Minimize the logic function

F(A,B,C,D) = II M (1,2,3,8,9,10,11 ,14). d (7,15)

Use Karnaugh map. Draw the logic circuit for the simplified function using NOR gates only

6.     What is the necessity of interfacing in digital ICs and what are the points to be kept in view, while interfacing between TTL gate and CMOS gate?

Section –C

7.       

a.     What is multiplexer Tree? Why it needed? Draw the block diagram of a 32:1 Multiplexer Tree and explain, how is input directed to the output in this system.

b.     What is  a Decoder? Compare a decoder and a demultiplexer with suitable block diagrams.

8.       

a.     Draw the logic diagram of 4-bit Twisted Ring counter and explain its operation with the help of timing diagram

b.     Design a MOD – 3 Susnchronous counter using J-K flip-flops.

9.       

a.     Differentiate between static MOS and Dynamic MOS RAM. Draw the circuit of a static MOS RAM cell and explain its working.

b.      The capacity of 2K x 16 PROM is to be expand to 16 K x 16. Find the number of PROM chips required and the number of address lines in the expanded memory.