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A demultiplexer(DEMUX) performs the reverse operation of a multiplexer. It takes input from one line and distributes it to a given number of output lines. It is also known as a data distributor. A demultiplexer with 2n output lines should have n data-selector lines.

1:4 Demultiplexer

A 1:4 demultiplexer takes input from one line and distributes it to 4 output lines. It has 2 data selector lines.

1x4 demultiplexer block diagram

The operation of a 1:4 demultiplexer is described in the truth table.

Data Selector Outputs
S1 S0 Y3 Y2 Y1 Y0
0 0 0 0 0 I
0 1 0 0 1 0
1 0 0 I 0 0
1 1 I 0 0 0

The logical expression can be derived from the truth table.


It can be implemented using the following circuit.

1x4 demultiplexer circuit

The data input lines go to all of the AND gates. The two data-selector lines enable only one gate at a time based on its value.

if S1=0 and S0=0 then the data input is distributed to the Y3 output line and the value of all other output lines will be 0.

Further Reading

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