**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]