B.E. (Fourth semester) EXAMINATION,JUNE, 2008
(Common for EC/EE/EX Engg.)
(DIGITAL CIRCUIT AND SYSTEM)
Note: Attempt any five questions. All question carry equal marks.
1 (a) Convert the following:
(i) (27.125)10= ( )8=( )2 (ii) (237)8=( )10
(iii) (249)10=( )16= ( )2 (iv) (20.305)10=( )BCD
(b) Prove the following using De Morgen’s theorem:
(A+B)(C+D) =(A+B)+ (C+D)
And hence that one OR-AND configuration is equivalent to NOR- NOR configuration. Realize the
logical equation above using :
(i) OR and gates (ii) Only NOR gates
2 (a) Minimize the following logic function using K-map and realize using NAND gates:
(b) Design a full adder and derive the expressions for output and realize it with NAND gates.
3 (a) Explain the operation of look ahead carry generator.
(b) Explain the working of a 4-bit parallel binary adder.
4. (a) Explain the working of Schmitt trigger square wave generator .
(b) Explain the operation of the RTI NOR gate.
5. (a) Explain a Synchronous 4-bit up-down counter.
(b) What is shift register? How a word is stored in a serial shift resister?
6. (a) Explain ROM and its working . How is different from PLA.
(b) Implement the given Boolean function with 8×1 multiplexer:
7 (a) Draw the block diagram of successive approximation A to D converter and explain its operation.
(b) Design BCD to excess-3 code converter circuit and draw the logic diagram.
8 Write short notes on any two of the following :
(i) BCD adder (ii) Astable multavibrator (iii) Decoder and encoder (iv) Sample and hold circuit
(v) TTL circuits