Download GTU (Gujarat Technological University Ahmedabad) B.Tech/BE (Bachelor of Technology/ Bachelor of Engineering) 2020 Summer 3rd Sem 3131704 Digital Electronics Previous Question Paper

Enrolment No.___________

**GUJARAT TECHNOLOGICAL UNIVERSITY**

**BE - SEMESTER? III EXAMINATION ? SUMMER 2020**

**Subject Code: 3131704**

**Date:02/11/2020**

**Subject Name: DIGITAL ELECTRONICS**

**Time: 02:30 PM TO 05:00 PM**

**Total Marks: 70**

**Instructions:**

**1. Attempt all questions.**

**2. Make suitable assumptions wherever necessary.**

**3. Figures to the right indicate full marks.**

**MARKS**

**Q.1**

**(a)**Design a logic circuits for AND,OR and NOT gate using only

**03**

NAND gates.

**(b)**What is the difference between demultiplexer and multiplexer ?

**04**

Explain with necessary diagram and truth table.

**(c)**Explain D flip flop in detail with circuit diagram and truth table

**07**

**Q.2**

**(a)**Derive the SOP expression for following term

**03**

AB'C' + ABC' + AB'CD + A'BC' + AB

**(b)**Explain binary to gray and gray to binary conversion with

**04**

circuit diagram and truth table.

**(c)**Minimize the following function using tabulation method:

**07**

F(w, x, y, z) = (0,1,2,8,10,14,15)

**OR**

**(c)**Design a logic circuit for half and full subtraction circuits with

**07**

K-map equations and truth table.

**Q.3**

**(a)**Convert the following numbers to decimal:

**03**

(10101.101)2 , (330.4)8 , (A325)16

**(b)**Construct 3x8 decoders with diagram and necessary truth table.

**04**

**(c)**Explain following terms with example

**07**

1) Inter register-transfer operation

2) Arithmetic micro operation

3) Shift micro operation

4) Logic micro operation

**OR**

**Q.3**

**(a)**

Dr

aw the circuit of 3 input TTL(Transistor Transistor Logic)

**03**

NAND gate and explain its operation.

**(b)**

Explain working of 4-bit binary ripple counter.

**04**

**(c)**

Simplify the following equation using K-map and

**07**

implement using logic gates:

F(A,B,C,D) = (0,1,2,3,5,7,8,9,10,12,13)

**Q.4**

**(a)**

Explain BCD adder with diagram and truth table

**03**

**(b)**Explain 1's and 2's complement with example

**04**

**(c)**

Explain 2-bit UP synchronous counter with K-map

**07**

equations and circuit diagram

**OR**

**Q.4**

**(a)**Write short note on PLA.

**03**

**(b)**Reduce the expression A+B[AC+(B+C')D]=A+BD

**04**

**(c)**With neat sketch explain the operation of clocked RS flip flop

**07**

with NAND and NOR gates.

1

**Q.5**

**(a)**Represent the decimal number 8620 in BCD, Excess-3, and

**03**

Gray code.

**(b)**Explain 2 bit magnitude comparator with necessary diagram

**04**

and equation.

**(c)**

List out different types of memories used in digital logic

**07**

circuits and define them.

**OR**

**Q.5**

**(a)**Explain meaning of following micro operations

**03**

1) T1 : A+B'+1

2) T2 : A B

3) T3 : shr A

**(b)**Explain BUS transfer logic for two registers

**04**

**(c)**Design a logic circuit with JK flip-flop flip flop for the given

**07**

state sequence with necessary K-map equation

Present state

Next state

000

001

001

010

010

011

011

100

100

101

101

000

*****************

2

This post was last modified on 04 March 2021