# Demultiplexer

A demultiplexer (or demux) is a device that takes a single input line and routes it to one of several digital output lines. A demultiplexer of 2n outputs has n select lines, which are used to select which output line to send the input. A demultiplexer is also called a data distributor.

Demultiplexers can be used to implement general purpose logic. By setting the input to true, the demux behaves as a decoder.

The reverse of the digital demultiplexer is the digital multiplexer

## 1 to 4 demultiplexer

A 1 to 4 multiplexer uses 2 select lines (S0, S1) to determine which one of the 4 outputs (Y0 - Y3) is routed from the input (D). Its characteristics can be described in the following simplified truth table.

Notes:
• Change the select inputs S1, S0
• Change the input and observe that it is routed to the selected output (Y0 - Y3)
• Larger demultiplexers can be constructed by chaining smaller demultiplexers together. Click on the 1 to 4 DEMUX sub circuit to see that it is made up of 3 cascading 1 to 2 DEMUX.

Learn by Doing

Design a 1 to 4 Demultiplexer to further your understanding of the circuit.

## 1 to 2 demultiplexer

A 1 to 2 demultiplexer uses 1 select line (S) to determine which one of the 2 outputs (Y0, Y1) is routed from the input (D). Its simplified truth table is:

Note the full truth table that describes the 1 to 2 DEMUX completely

Learn by Doing

Design a 1 to 2 Demultiplexer to further your understanding of the circuit.