UNIVERSITY EXAMINATIONS: 2018/2019
EXAMINATION FOR THE BACHELOR OF SCIENCE IN INFORMATION
SECURITY AND FORENSICS
BISF1208 SEMICONDUCTOR & ELECTRONIC DEVICES
DATE: APRIL, 2019 TIME: 2 HOURS
INSTRUCTIONS: Answer Question 1 AND any other TWO questions.
QUESTION ONE (COMPULSORY)
Define the following terms [10 Marks]
(i) doping
(ii) n-type semiconductor
(iii) binary
(iv) position value number system
(v) radix
(vi) complement
(vii) K-Map
(viii) truth table
(ix) logic gate
(x) logic level
b) Perfom the following conversions [6 Marks]
(i) 100101001(2) to Octal
(ii) 347.317(8) to HEX and binary
(iii) 8F.3CE(16) to decimal and Octal
c) Using 2’s complement perform the following [3 Marks]
11001010 – 1100111
d) Explain how doping produces p-type semiconductor [4 Marks]
e) A comparator circuit has the following design parameters: the circuit compares two bits A and B
and gives the output z(A=B), y(A>B) and x(B>A). Construct the comparator circuit. Show all the
steps and working [7 Marks]
QUESTION TWO
a) Give the logic gates and truth tables of XOR and XNOR [6 Marks]
b) Use a K-Map to minimize the following expression [6 Marks]
F(A,B,C,D) = ∑m(0,3,4,5,7,9,11,12,14,15)
c) Explain the difference between analogue and digital systems [4 Marks]
d) Draw the circuit diagram of the following expression [4 Marks]
F=A’C + BC’ + A’B’C’ + A’B
QUESTION THREE
a) Starting with the truth table show the construction of a full adder (3 bit adder) [10 Marks]
b) Give the truth table and symbols of the three basic gates [6 Marks]
c) Give four advantages of semiconductor based digital systems [4 Marks]
QUESTION FOUR
a) Simplify the logic circuit below using boolean algebra [10 Marks]
F(A,B,C,D) = A’B’C’D’ + A’B’C’D + A’B’CD + A’B’CD’ + A’BC’D’ + A’BC’D +
AB’C’D + ABCD + ABC’D
b) Describe the difference between combinational and sequential logic [2 Marks]
c) Describe the following flip flops and their application [8 Marks]
(i) SR
(ii) D
QUESTION FIVE
a) Describe the construction and use of the following logic devices [12 Marks]
(i) pn junction diode
(ii) BJT – bipolar junction transistor
(iii) LED – light emitting diode
b) Outline two practical semiconductor circuits used in computer security [4 Marks]
c) Briefly outline the steps of analogue to digital conversion of signals (a waveform diagram may be
used) [4 Marks]
