EEB603: Digital Electronics
Lab: 07
Student Name:
Ritikh Deo: S2019006042
Section
Content
Typical Mistakes
Marks
[Mark]
Deducted
1. Objective
[1 marks]
 Objective
 Significance of experiment
 Objective is not stated or not clear
2. Theory
[2 marks]
 Explanation of theory
 Inadequate explanation of theory
3. Procedure
[2 marks]
 Outline the step by step procedure
for the experimental study
 Equations or symbols are incorrect or not defined
properly
 Past tense not used
 Passive voice not used
 Important information and/or details on data
collection missing or stated incorrectly
 Diagrams missing/not labeled/not clear
4. Observation and
results
[8 marks]
 Show all relevant tables and graphs
illustrating results
 Provide appropriate error analysis
example calculations
 Provide a comparison of
experimental results with the
accepted value
 Observations/results are incorrect or units are
missing
 Data tables or graphs are incorrect or not properly
labeled and numbered
 Example calculations are not included or not
clearly explained
 Clear contradiction between the observed data
and the results/conclusions
 Percentage error calculations (if any) are missing
5. Discussion and
Conclusions
[4 marks]
 Discuss the results (range, trends,
sources of errors)
 Present conclusions based on the
results
 Answer discussion questions
 Sources of errors (if any) are not clearly explained
6. References
[1 mark]
 State complete references to any
books, articles, websites, etc. from
which information is obtained
 Indicate in the appropriate places in
the body where these references
are used.
7. Grammar and
Structure
[2 mark]
 The report should be neat and well
structured
 Proper grammar should be used
8. Submission
 Timely submission
 Conclusion is merely a repetition of discussion
 Conclusion
not
sensible/supported
by
experimental evidence
 Discussion questions are incorrect/partially
correct/not answered
 References are not used
 Incomplete references
 References do not point to the place in the report
where the source were used
 Grammatical errors
 Structure of report is not as per template
 Late submission
s
Total Mark Awarded
[20 marks]
1|Page
EEB603: Digital Electronics
Lab: 07
Title: Multiplexers and Demultiplexers
Aim: To design and implement a system that will realize the two exclusive functions, f1 and f2 as given in the table
below, using the following;
(a) 74LS153 Dual 4-to-1 Multiplexer,
(b) 74LS138 3-to-8 Decoder.
Introduction:
In the large scale digital systems, a single line is required to carry on two or more digital signals. At a time, one
signal can be placed on the one line. But, what is required is a device that will allow us to select; and the signal we
wish to place on a common line, such a circuit is referred to as multiplexer.
Multiplexer is a device that has multiple inputs and a single line output. The select line determine which input is
connected to the output, and also to increase the amount of data that can be sent over a network within certain
time. It is called a data selector. De-multiplexer is also a device with one input and multiple output lines. It is used
to send a signal to one of the many devices.[1]
https://www.elprocus.com/what-is-multiplexer-and-de-multiplexer-type-and-its-applications/
Materials:
DC Power Supply
IC’s – 74LS138, 74LS153, 74LS04
Resisterss-3 x 1kΩ, 2 x 330Ω
LEDs-Red, Green
DIP Switch
Probe
Procedure:
Two mutually exclusive control circuits are described by the Boolean functions, f1 and f2 in Table 01.
Multiplexer Design
The 74LS153 Dual 4-to-1 Multiplexer was used to realize the two functions where only one function was to be
active at any one time, and not both. Note that the 74LS153 has an ‘Enable” control line which is used to control
the desired output, f1 or f2. This circuit was implemented using the multisim software.
Decoder Design
The two functions were realized using the 74LS138 3-to-8 Decoder/Demultiplexer. Only one function had to
be active at one time. Note that the 74LS138 has an ‘Enable” control line which is used to control the desired
output, f1 or f2. . This circuit was implemented using the multisim software.
The option 1 has been chosen to be implemented.
Table 01.
2|Page
EEB603: Digital Electronics
Lab: 07
Results:
Multiplexer Design
Truth Table:
Table 02:
0
1
2
3
4
5
6
7
S1
A
0
0
0
0
1
1
1
1
S0
B
0
0
1
1
0
0
1
1
C
0
1
0
1
0
1
0
1
f1
1
1
0
1
0
0
1
0
0
1
2
3
4
5
6
7
S1
A
0
0
0
0
1
1
1
1
S0
B
0
0
1
1
0
0
1
1
C
0
1
0
1
0
1
0
1
f2
0
1
1
0
1
1
0
0
From the Truth table and with CB = S1S0, the inputs (In) to the Mux will hold the data summarized in Table 3
below:
Table 03.
Data(f1) Inputs
1
C
0
C
Data(f2)
C
C
1
0
I0
I1
I2
I3
Inputs
I0
I1
I2
I3
E (Enable)
74LS153
1
C
0
C
A
B
C
C
1
0
I3a
I2a
I1a
I0a
S1
S0
I3b
I2b
I1b
I0b
Ea
Ya
Yb
Eb
3|Page
EEB603: Digital Electronics
Lab: 07
Note:
When E (Enable) = 0, Ea is enabled, but Eb is disabled. The values of A and B will then select which of I a inputs will be
outputs to f1.
When E (Enable) = 1, Eb is enabled while Ea is disabled. The values of A and B will then select which of the I b inputs
will be output to f2.
Decoder Design
Truth Table:
Table 04.Consider the truth table again.
Selectors
A B C
0 0 0
0 0 1
0 1 0
0 1 1
1 0 0
1 0 1
1 1 0
1 1 1
0
1
2
3
4
5
6
7




f1
1
1
0
1
0
0
1
0
0
1
2
3
4
5
6
7
Selectors
A B C
0 0 0
0 0 1
0 1 0
0 1 1
1 0 0
1 0 1
1 1 0
1 1 1
f2
0
1
1
0
1
1
0
0
All minterms of f1 and f2 having value of ‘1’ are selected.
The minters of f1 having the value of 1 are OR’ed to form f1’ and similarly minterm of f2 having a value of 1
are OR’ed to form f2.
As the output of the 74LS138 are active LOW, all outputs are connected to an Inverter, hence to an OR
gate. Using De Morgan’s theorem, this is equivalent to a NAND gate.
Eg.
A+B+C (De Morgan’s theorem) = ABC (NAND gate)
F1 is enabled when E =0(and f2 is disabled).f2 is enabled when E=1(and f1 is disabled)
74LS138
A
B
C
A2
A1
A0
E3
E2
E1
Q7
Q6
Q5
Q4
Q3
Q2
Q1
Q0
f1
f2
4|Page
EEB603: Digital Electronics
Lab: 07
Discussion:
The main difference between a multiplexer and a de-multiplexer is that a multiplexer takes two or more signals
and encodes them on a wire, whereas a de-multiplexer does reverse to what the multiplexer does.
Conclusion:
To conclude, multiplexer is used in various applications wherein multiple data can be transmitted using a
single line.Demultiplexer has one input and multiple outputs.
Reference:
[1].What is Multiplexer and De-multiplexer
https://www.elprocus.com/what-is-multiplexer-and-de-multiplexer-type-and-its-applications/
5|Page