Page 69 - Digital Electronics by harish

Applications of MUX

Multiplexers are used to implement combinational logic functions.

The function , , = (1, 3, 5, 6) can be implemented using an 8-1 multiplexer, as
shown in figure.

1 0

0
1
2
3 8 : 1 Y
4 MUX
5
6
7
S 1 S 2 S 3
A
B
C

The variables A, B and C are applied to the select lines. The minterms to be included (1, 3, 5
and 6) are chosen and their corresponding input lines are connected to 1 (Vcc). The
remaining input lies (0, 2, 4 and 7) are connected to 0 (GND). When the select lines ABC are
000, the input line 0 is selected and we get 0 at the output because the input line 0 is
connected to GND. Similarly, when the select lines ABC are 101, the input line 5 is selected
and we get 1 at the output because the input line 5 is connected to Vcc.

2.13 Demultiplexer (DEMUX)

Demultiplex means „one to many‟. A demultiplexer is a logic circuit with only one input and
many outputs. We can send the data input to any one of the outputs by using the control input
signals. Demultiplexer is also called „data distributer‟.

Figure :Demultiplexer

m
m
If there are „m‟ select lines, we can have a maximum of 2 output lines. Hence, n ≤ 2 .

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