VTU Previous Year Question Papers EC 3rd Semester Logic design July 2008

VTU Previous Year Question Papers EC 3rd Semester

Logic design July 2008


Note : Answer any FIVE full questions, choosing at least two from each part.


1 a. What are universal gates? Implement the following function using universal gates only ((A + B)c)d

b.  Simplify the following using K – map F(A, B, C, D) ~ ABC + AD + BD + CD + AC + a5 .

c.   What are the drawbacks of k-map? Simplify the following expression using Quine – Me Clusky Method. F(A, B, C, D) = S(l,2,8,9,l 0,12,13,14).


2    a. Show that using a 3 – to – 8 decoder and multi -input OR gate. The following Boolean expressions can be realized. F1(A,B,C) = £m(0,4,6), F2(A,B,C)= £111(0,5), F3,(A,B,C)= Em(l,2,3,7).

b. Design Decimal – to – BCD encoder?

c.   What are the different types of PLD’s and implement the 7 – segment decoder using PLA?

d.   Write a verilog code for 4 : 1 multiplexer using case statement.


3 a. i) Perform 8 – bit addition of the decimal numbers – 28 and + 15 in 2’s complement.

ii) Perform 8 – bit subtraction of the decimal numbers – 28 and + 65 in 2’s complement.

b.  i) Find the binary addition of (7510)io and (538)io using 16 – bit numbers

ii) Find the binary subtraction of (2QO)io and (125)io using 8 – bit numbers.

c.   Explain the binary Adder – subtracted circuit with an example.


4  a. What is Schmitt trigger? Explain Schmitt trigger transfer characteristic.

b. Explain the different types of flip fops along with their truth table. Also explain the race-around condition in a flip flop,

c. Differentiate between combinational circuit and sequential circuit.


5    a. Explain a 4 -bit serial input shift registers in detail and give its timing diagram.

b.   Design a mod – 5 synchronous up counter using JK flip flop.


6 a. Explain Moore model with state synthesis table and also obtain the circuit diagram for Moore model.

b.   Design an asynchronous sequential logic circuit for state transition diagram shown in Fig.


Q 6(b).

7 a. What is a binary ladder? Explain the binary ladder with a digital input of 1000.

b.   Explain a 2 – bit simultaneous A/D converter.


8 a. With a circuit diagram, explain the operation of the CMOS NAND gate.

b.   Explain a 2 – input NAND gate TTL with Totem – pole output with a neat

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