# Different Types of Demultiplexers

A Demultiplexer is a data distributor read as DEMUX. It is quite opposite to multiplexer or MUX. It is a process of taking information from one input and transmitting over one of many outputs. This article explains different types of Demultiplexers.

DEMUX are used to implement general-purpose logic systems. A demultiplexer takes one single input data line and distributes it to any one of a number of individual output lines one at a time. Demultiplexing is the process of converting a signal containing multiple analog or digital signals backs into the original and separate signals. A demultiplexer of 2^n outputs has n select lines.

## Types of Demultiplexers

### 1 to 4 Demultiplexer

The 1 to 4 demultiplexer consists of one input, four outputs, and two control lines to make selections The below diagram shows the circuit of 1 to 4 demultiplexer.

The input bit is Data D with two select lines A and B. The input bit D is transmitted to four output bits Y0, Y1, Y2, and Y4.

When AB is 01 The upper second AND gate is enabled while the other AND gate is disabled. Thus, only one data is transmitted at Y1. If D is low, then Y1 is low and if D is high, Y1 is high. The value of Y1 depends on the value of D.

If the control input changes to AB=10 all the gates are disabled except the third AND gate from the top. Then D is transmitted to output Y2.

#### Truth Table

The below is the truth table for the 1 to 4demultiplexer.

### 1 to 8 Demultiplexer

A 1 to 8 demultiplexer consists of one input line, 8 output lines and 3 select lines. Let the input be D, S1 and S2 are two select lines and eight outputs from Y0 to Y7. It is also called as 3 to 8 demux because of the 3 selection lines. Below is the block diagram of 1 to 8 demux.

#### Truth Table

The below is the truth table for 1 to 8 demultiplexer. It tells the functionality of the demux, like, if S1S2S0=000, then the output is seen at Y0 and so on.

Using the above truth table the logic diagram of the demultiplexer is implemented using eight AND and three NOT gates. The different combinations of the select lines select one AND gate at given time, such that data input will be seen at a particular output.

A 1 to 8 demultiplexer can be implemented using two 1 to 4 demultiplexers. Implementation of large output demultiplexers becomes complex, so smaller demux is used to implement large demultiplexers.

### 1 to 16 Demultiplexer

1 to 16 demultiplexer has one input data, four select lines A, B, C and D and 16 output lines Y0 to Y15. This is implemented using AND and NOT gate. 1 to 16 demultiplexer is implemented using the logic circuit below.

This can be implemented using 1 to 8 demultiplexer, 1 to 4 demultiplexer and 1 to 2 demultiplexer.

#### Truth Table

The below truth table shows the operation of 1 to 16 demultiplexer.

### Applications of Demux

• A demultiplexer is used to connect a single source to multiple destinations. Demultiplexers are mainly used in the field of the communication system.
• Demultiplexers are used for the reconstruction of parallel data and ALU circuits.
• The demultiplexer receives the output signals of the multiplexer and converts back to the original form of the data at the receiving end. MUX and DEMUX work together to carry out the process of communication.
• Demultiplexer helps to store the output of the ALU in multiple registers and storage units in an ALU circuit. The output of the data the ALU is fed as data input to the DEMUX. Each output of the DEMUX is connected to the multiple registers which can be stored in the register.
• A serial to parallel converter is used for reconstructing the parallel data from the incoming serial data stream. In this technique, serial data from the incoming serial data stream is given as the input to the DEMUX at regular intervals. A counter is attached to the control input of the demux. This counter directs the data signal output of the demux where these data signals are stored. When all data signals have been stored. The output of the demux can be retrieved and read out in parallel.