**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]