Punjab University 2005 B.Tech Electronics and Communications Engineering DIGITAL ELECTRONICS - Question Paper

DIGITAL ELECTRONICS
Max Marks 60
Note:- This paper consist of 3 parts part A is compulsory. Do any 4 ques. from Secion B and any 2 ques. from part C.

Section-A Marks:20
(10 *2 =20)
1.(a) Application of ASCII ,Excess-3 and grey codes.
(b) Differentiate ranging from combinational and sequential circuits.
(c) the advantages of edge triggered flip-flops
(d) How subtraction of 4-bit no. is performed by addition?
(e) If 2 inputs are to be used for a four input NAND gate, explain the choices avalable with the unused inputs.
(f) A/D accuracy and resolution
(g) Fan in, Fan out, propagation relay terms related to logic gates.
(h) Special features of content addressable memories.
(i) Advantages and disadvantages of synchronous over asynchronous counters.
(j) Conversion of 100.55(10) into binary, octal codes.

Section-B Marks : five every
(5 * 4=20)
2. Draw the circuit of a three to eight decoder and discuss its operation. How this can be used as a DEMUX.
3. obtain the complement of the boolean function and decrease it to a minimum number of literals :
B'D+A'BC'+ACD+A'BC.
4. Draw the circuit of a negative edge triggered J-K flip flop with d.c. pre-set and d.c. clear choices using S-R flip flops
and explin its truth table.
5. Draw and explain the circuit of a dual scope A/D convertor.
6. Draw the circuit of a 3- input TTL totem pole NAND gate and discuss its operation.

Section-C Marks:10 every
(10 *2 =20)
7.(a) Mention the different A/D converters. Discus the comparison of advantages and disadvantages of every of these.
(b) Simple using Q-M method:
X(A,B,C,D)= SIGMA(0,1,2,8,10,11,14,15).
8.(a) Draw the circuit of Ecl gate and discuss its operation.
(b) explain the comparison of the important characteristics of the different IC logic families.
9.(a) Draw the circuit of a BJT RAM cell and discuss its operation
(b) Draw the circuit of a 4-bit shift register and discuss its operation.

Earning:   Approval pending.