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 2^{n} 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.

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

Data Selector | Outputs | ||||
---|---|---|---|---|---|

S_{1} |
S_{0} |
Y_{3} |
Y_{2} |
Y_{1} |
Y_{0} |

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.

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 S_{1}=0 and S_{0}=0 then the data input is distributed to the Y_{3} output line and the value of all other output lines will be 0.