B.E. (Fourth semester) EXAMINATION, DEC, 2008
(Common for EC/EE/EX Engg.)
(DIGITAL CIRCUIT AND SYSTEM)
Note: Attempt any five questions. All question carry equal marks.
1 (a) (i) Add (25)8and (66)8
(ii) Subtract (7 B) 16and (A 3)16
(iii) Represent the decimal number 25 in binary from using
(1) BCD (2) Gary code (3) Hexadecimal code (4) Excess-3 code (5) Octal code
(6) Binary code
(b) Simplify the Boolean function F in sum of products using the don’t care conditions d:
(i) F= Y’+X’z’ (ii) F= B’C’D+B C D’+ ABCD’
d=Yz+xy d=B’CD’+A’B C’D
2 (a) Simplify each of the following function and implement then with NAND gates:
(i) F1 = A C”+A C E+A C E’ +A’CD’ +A’D’E’
(ii) F2=(B’+D’)( A’+C’+D’)(A+ B’+C’+D’) (A’+B’+C’+D’)
(b) Design a multiple- output logic circuit using the following function:
t1 =?m(2,3,7,10,11,14)+ d(1,5,15)
t2 =?m(0,1,4,7,13,14) + d (5,8,15)
3 (a) Obtain and NAND logic diagram of a full adder from the Boolean Function:
(b) Describe the design of parallel adder.
4 (a) Describe the half –subtractor and full-subtractor.
(b) Draw the logical diagram of Look-Ahead carry generator and describe also.
5 (a) Describe the monostable and astable multavibrator using IC 555 Timer.
(b) Explain the following characteristics parameters of digital ICs:
(i) Speed of operation (ii) Current and Voltages rating (iii) Power Dissipation
(iv) Figure of merit (v) Noise immunity
6 (a) Why interfacing is required? How TTL can Interface with MOS?
(b) Describe the Emitter-Coupled logic for-3 inputs OR/NOR gate.
7 (a) Write short notes on semiconductor memories.
(b)Discribe the BCD ripple counter.
8 (a) Explain the multiplexer and demultiplexer.
(b) Design BCD to Excess-3 code converter using Gates.
9 (a) Define the Accuracy and resolution in D/A Converter. What is the resolution of a 9-bit D/A
converter which uses a ladder network? Also express in percent. If the full scale output voltage of
this converter is +5, what is the resolution in volts?
(b) Describe the practical D/A converter.
10 (a) Describe the sample and hold circuit.
(b) Explain the counter type A/D converter. Suppose counter type A/D Converter is an 8 -bit
converter and driven by KHz clock find:
(i) Maximum Conversion time (ii) Average Conversion time (iii) Maximum conversion rate