4EC3 Digital Electronics

Submission date:-24-03-08

1. (a) Obtain the reduced simplified Boolean expression for output F & G in terms of input variables.

(b) Design a full-subtractor circuit with inputs x and y outputs D and B. The circuit subtracts x – y – z, where z is the input borrow, B is the output borrow, and D is the difference.

2. (a) Design a 16x1 multiplexer using

(i) 8x1 multiplexer

(ii) 4x1 multiplexer

(iii) Two 8x1 multiplexer & One 2x1 multiplexer.

(b) Implement the following Boolean function with

(i) 4x1 multiplexer

(ii) 8x1 multiplexer

F (A,B,C,D) = ∑m (1,3,4,11,12,15)

3. (a) Design a BCD adder/ substractor circuit

(b) Design a combinational circuit that compares two 4 bit numbers.

4. (a) Draw the logic diagram of a 2 to 4 line decoder using ‘NOR’ gates only. Include the enable input.

(b) Design a 4 bit priority encoder in which Input D_o has the highest priority & D₃ has the lowest priority.

5. (a) Implement the full adder with two 4x1 multiplexer.

(b) Design a combinational circuit that converts a 4 bit Gray code to a 4-bit binary number. Implement the circuit with exclusive-OR gates.

6. (a) Design a code converter that converts a decimal digit from the 8,4,-2,-1 code to BCD.

(b) Design the BCD-to-seven-segment decoder using a minimum number of gates.

7. (a) Convert the RS Flip Flop to JK Flip Flop. Draw the schematics siagram of JK flip Flip Flop obtained after the conversion from RS Flip Flop.

(b) What is the race around condition? How the problem of race around condition is avoided in JK master slave JK Flip Flop.

8. Write short notes on the following:

(i) Difference between JK & RS flip flop

(ii) Difference Between encoder, decoder, multiplexer & demultiplexer.

(iii) Difference between combinational circuit & sequential circuits.

9. (a) Show that the characteristic equation for the complement output of a JK flip flop

Q = J Q + K Q

(b) Explain the difference among truth table, a state table, a characteristic table, and an excitation table.