MULTIPLEXER Circuit is a data selector. It is a device that selects between several analog or digital input signals and forwards the selected input to a single output line.

1. MULTIPLEXER(MUX)
A P R ES E N TAT I O N A B O U T M U LT I P L E X I N G
Mehedi Hasan
CSE, DIU
(b-74)

2. Index
• Introduction
• A Closer look at Multiplexer
• Implementing minterm function in MUX
• Circuit Diagram
• De-MUX

3. Intro_
Multiplexing
Multiplexing is the process of combining one or more signals and transmitting on a single channel. In analog communication systems, a
communication channel is a scarce quantity, which must be properly used. For cost-effective and efficient use of a channel, the concept of
Multiplexing is very useful as it allows multiple users to share a single channel in a logical way.
The three common types of Multiplexing approaches are:
1. Time
2. Frequency
3. Space
Two of the best examples of Multiplexing Systems used in our day-to-day life are the landline telephone network and the Cable TV.

4. A Closer look at Multiplexer
What is Multiplexer
A Digital Multiplexer is a combinational circuit that select a Binary information from one of many input lines and more than one select line.
The multiplexer or MUX is a digital switch, also called as data selector. The basic idea of multiplexing is shown in figure below in which data
from several sources are routed to the single output line when the enable switch is ON. This is why, multiplexers are also called as ‘many to
one’ combinational circuits.
If there are m selection lines, then the number of possible input lines is 2m. Alternatively, we can say that if the number of input lines is
equal to 2m, then m selection lines are required to select one of n (consider 2m = n) input lines.
This type of multiplexer is referred to as 2n × 1 multiplexer or 2n-to-1 multiplexer. For example, if the number of input lines is 4, then two
select lines are required. Similarly, to select one of 8 input lines, three select lines are required.

5. Implementing min-term function in MUX
Boolean function implementation
Any n-variable logic function can be implemented using a smaller 2n-1-to-1 multiplexer and a single inverter.
D.Q. Implement the function F(X,Y,Z) = S(1,3,5,6) using an 8-to-1 mux.
Connect the input variables X, Y, Z to mux select lines. Mux data input lines 1, 3, 5, 6 that correspond to the function min-terms are
connected to 1. The remaining mux data input lines 0, 2, 4, 7 are connected to 0.

6. Implementing min-term function in MUX
X Y Z F
0 0 0 0
0 0 1 1
0 1 0 0
0 1 1 1
1 0 0 0
1 0 1 1
1 1 0 1
1 1 1 0
In the 8 to 1 multiplexer, there are total eight inputs, i.e., A0, A1, A2, A3, A4,
A5, A6, and A7,
3 selection lines, i.e., X, Y and Z and single output, i.e., F.
On the basis of the combination of inputs that are present at the selection
lines X, Y, and Z, one of these 8 inputs are connected to the output. The
block diagram and the truth table of the 8×1 multiplexer

7. Circuit Diagram

8. De-Multiplexer
A De-multiplexer is a combinational circuit that has only 1 input line and 2N output lines. Simply, the multiplexer is a single-input and multi-
output combinational circuit. The information is received from the single input lines and directed to the output line. On the basis of the
values of the selection lines, the input will be connected to one of these outputs. De-multiplexer is opposite to the multiplexer.
Unlike encoder and decoder, there are n selection lines and 2n outputs. So, there is a total of 2n possible combinations of inputs. De-
multiplexer is also treated as De-mux.
Block Diagram

9. Implementing min-term function in De-MUX
1×8 De-multiplexer
In 1 to 8 De-multiplexer, there are total of eight outputs, i.e., Y0, Y1, Y2, Y3, Y4, Y5, Y6, and Y7, 3 selection lines, i.e., S0, S1and S2 and single
input, i.e., A. On the basis of the combination of inputs which are present at the selection lines S0, S1 and S2, the input will be connected to
one of these outputs. The block diagram and the truth table of the 1×8 de-multiplexer

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