BACHELOR OF TECHNOLOGY IN ELECTRICAL AND ELECTRONICS
ENGINEERING
EET 3256: DIGITAL ELECTRONICS I
CAT I
DATE: 3RD JUNE, 2021
TIME: 60 MINUTES
INSTRUCTIONS: Answer all questions (Total marks=30 marks)
1. With examples, differentiate between analog and digital quantities
2. a) Convert 0.5610 to binary, ending at 7 bits after the binary point
b) Convert 2318 to a hexadecimal number
c) Convert 5910 to Xs-3 code and state one advantage of the Xs-3 code
3. Simplify the following Boolean expression:
(3 marks)
(2 marks)
(2 marks)
(3 marks)
(3 Marks)
4. Simplify the Boolean function
𝐹 (𝑤, 𝑥, 𝑦, 𝑧) = (1, 3, 7, 11, 15)
which has the don’t-care conditions
𝑑 (𝑤, 𝑥, 𝑦, 𝑧) = (0, 2, 5)
(4 marks)
5. Draw a waveform to represent the logic levels High(1) and Low (0) at output Y in Fig.
Q(5a). Fig. Q(5b): shows the waveforms of the input A and B.
(2 marks)
(a)
(b)
Fig. Q(5)
6. Describe how to hardware-implement a four-input OR gate using two-input OR gates
only.
(3 Marks)
7. For the logic circuit shown in Fig. Q(7):
i.
Fig. Q(7)
Determine the output (in terms of Boolean expressions) of all four logic gates in
circuit
(2 Marks)
Page 1 of 2
ii.
Complete a truth table for the circuit and from this derive the ‘sum of products’
expression.
(3 Marks)
8. Suppose a design problem results in a minimized product of sums expression:
𝑥 = (𝐴 + 𝐵) (𝐵 + 𝐶) (𝐴 + 𝐶)
Implement this expression using NOR gates only.
(3 Marks)