Function of Multiplexers

A multiplexer is a circuit that accepts many input but give only one output. A demultiplexer function exactly in the reverse of a multiplexer, that is a demultiplexer accepts only one input and gives many outputs. Generally multiplexer and demultiplexer are used together, because of the communication systems are bi directional.

Multiplexer means many into one. A multiplexer is a circuit used to select and route any one of the several input signals to a signal output. A simple example of an non electronic circuit of a multiplexer is a single pole multi-position switch.

Multi-position switches are widely used in many electronics circuits. However circuits that operate at high speed require the multiplexer to be automatically selected. A mechanical switch cannot perform this task satisfactorily. Therefore, multiplexer used to perform high speed switching are constructed of electronic components.

Multiplexer handle two type of data that is analog and digital. For analog application, multiplexer are built of relays and transistor switches. For digital application, they are built from standard logic gates.

The multiplexer used for digital applications, also called digital multiplexer, is a circuit with many input but only one output. By applying control signals, we can steer any input to the output. Few types of multiplexer are 2-to-1, 4-to-1, 8-to-1, 16-to-1 multiplexer.

Following figure shows the general idea of a multiplexer with N input signal, M control signals and one output signal.