UNIVERSITY EXAMINATIONS: 2018/2019
EXAMINATION FOR THE DEGREE OF BACHELOR OF SCIENCE IN
INFORMATION COMMUNICATION TECHNOLOGY
BCT1305 SEMICONDUCTOR AND DIGITAL LOGIC
FULL TIME/PART TIME
DATE: DECEMBER 2018 TIME: 2 HOURS
INSTRUCTIONS: Answer Question One & ANY OTHER TWO questions.
QUESTION ONE (COMPULSORY)
a) Define the following with reference to digital logic
i) Logic gate
ii) Truth table
iii) Logic diagram [6Marks]
b) Give the three major electrical and electronics quantities and state their units of measurement [3Marks]
c) Draw a well labelled circuit diagram of the NPN transistor [3Marks]
d) Briefly describe the following semiconductor devices
i) Diode
ii) Transistor
iii) Integrated circuit [6Marks]
e) Explain the different regions that the bipolar transistor can operate within [6Marks]
f) Define the following terms as used in Boolean algebra
i) Boolean identity
ii) Boolean expression
iii) Boolean operator [6Marks]
QUESTION TWO
a) Describe the negative half cycle of full ware bridge rectifier. [6Marks]
b) State any four characteristics of common base transistor configuration [4Marks]
c) State any four characteristics of the P-N junction region of a junction diode [4Marks]
d) Describe any three integration categories with reference to integrated circuits [6Marks]
QUESTION THREE
a) Perform the following number system conversions
i) 101101012 to decimal [3Marks]
ii) BA9716 to octal [4Marks]
iii) 468910 to hexadecimal [3Marks]
b) Perform the following using 2’s complement notation -83 + 115 [4Marks]
c) Give the logic symbols and truth tables of the following 3input logic gates
i) XOR gate
ii) NOR gate [6Marks]
QUESTION FOUR
a) Using De-Morgan’s laws prove that
X.Y.Z = X+ Y+ Z [4Marks]
b) i) Define a flip flop [2Marks]
ii) With the aid of a logic diagram and truth table describe the S-R flip flop [6Marks]
c) Simplify the following logic equation then draw the truth table of the simplified form
F (ABC) = A.B.C. + A. B. C. + A. B. C. + A. B. C. + A. B. C. [8Marks]
QUESTION FIVE
a) With the aid of a voltage and current characteristic graph, describe the operation of a Zener diode
[8Marks]
b) Differentiate between combinational and sequential circuits [4Marks]
c) Simplify the Boolean equation below using a karnaugh map (k-map) the draw the logic gate equivalent
of the simplified form
F(X,Y,Z) = X. Y. Z + X.Y.Z + X.Y.Z + X.Y.Z + X.Y. Z + X.Y.Z [8Marks]
