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Table of contents
1.
Introduction
2.
What is a Demultiplexer?
3.
Types of Demultiplexers
3.1.
1 x 2 Demultiplexer
3.2.
1 x 4 Demultiplexer
3.3.
1 x 8 Demultiplexer
3.4.
1 x 16 Demultiplexers
4.
Applications of Demultiplexer
5.
Advantages of Demultiplexer
6.
Disadvantages of Demultiplexer
7.
Frequently Asked Questions
7.1.
What is the main function of a demultiplexer?
7.2.
What is a 1 2 demultiplexer?
7.3.
What is demux with example?
7.4.
What is a 2 4 demultiplexer?
7.5.
Which IC is used for demultiplexer?
8.
Conclusion
Last Updated: Mar 27, 2024
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What is Demultiplexer (DEMUX)?

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Introduction

Multiplexers are combinational logic circuits in which one input is selected from many inputs and then passed to a single output. The device that facilitates multiplexing is known as the MUX.

demultiplexer

On the other hand, demultiplexers are the reverse of what multiplexers do by taking two or more signals. Demultiplexers are primarily used in Boolean function generators and decoders. Integrated circuits (ICs) are available in different input/output configurations for demultiplexer. In this article, we will discuss What is Demultiplexer(DEMUX)? in detail.

What is a Demultiplexer?

A demultiplexer, also known as Demux or data selector is a digital circuit that uses control signals to direct a single input signal to any one of the multiple output lines. Demultiplexers with 2n outputs are equipped with n select lines used to select which output line is to be sent. These demultiplexers are also known as data distributors.

General-purpose logic can be implemented using demultiplexers. If we set the input to true, the demultiplexer will behave like a decoder. 

Digital multiplexers work oppositely as digital demultiplexers.

Demultiplexers can also be cascaded together to generate multiple outputs.

Demultiplexer
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Types of Demultiplexers

Demultiplexers are classified into four types:

  • 1x2 demultiplexer
  • 1x4 demultiplexer
  • 1x8 demultiplexer
  • 1x16 demultiplexer

1 x 2 Demultiplexer

In a 1x2 demultiplexer, there is one input line, two output lines, and one select line by switching the input to one of the two output lines. The block diagram below shows a 1x2 demultiplexer with additional enable input.

1 x 2 Demultiplexer

The Truth Table of the 1x2 multiplexer is given below.

S

I1

I0

Low(0)

0

I

High(1)

I

0

In the case of Low select input, the input will go to O1, and in the case of High select input, the input will go to O2.

The Boolean function can be determined using the truth table:

O0 = S’ I
O1 = S I

 

The Circuit Diagram of 1x2 multiplexer:

A data stream flows from the input to the output line O0. When S = 1, the second AND gate become enabled, and the first AND gate become disabled, which results in data being passed to the O1 output.

Circuit Diagram of 1x2 multiplexer

1 x 4 Demultiplexer

In a 1x4 demultiplexer, there is a single input (I), two selection lines (S1 and S0), and four outputs (O0, O1, O2, and O3). Depending on the combination of lines selected, input data flows to one of the four outputs at a time.

This demultiplexer is also called a 2x4 Demultiplexer, which means that it has two select lines and 4 output lines. The block diagram of a 1x4 DEMUX is shown below.

1 x 4 Demultiplexer

The Truth Table of the 1×4 multiplexer is given below:

S1 S0 I O3 O2 O1 O0
0 0 0 0 0 0 0
0 0 1 0 0 0 1
0 1 0 0 0 0 0
0 1 1 0 0 1 0
1 0 0 0 0 0 0
1 0 1 0 1 0 0
1 1 0 0 0 0 0
1 1 1 1 0 0 0

In case of S0 = 0 and S1 = 0, data input is connected to output O0 and in the case of S0 = 0 and S1 = 1, the data input is connected to output O1.

The outputs are also connected to the inputs for the other two combinations of select lines. Here, 'I' indicates input data, O0, O1, O2, O3 are output lines, and S0 & S1 indicate select lines.

The Boolean function can be determined using the truth table:

O0 = S1’ S0’ I
O1 = S1’ S0 I
O2 = S1 S0’ I
O3 = S1 S0 I 

 

The Circuit Diagram of 1x4 Multiplexer

It can be implemented using four AND gates and two NOT gates. These lines select which AND gate is to be enabled at any given time. As well as the enable input which functions as a global enable input, meaning that the outputs are enabled only when the 'E' bit is HIGH.

 

Circuit Diagram of 1x4 Multiplexer

1 x 8 Demultiplexer

As shown below, the 1x8 demultiplexer has one input 'I,' three select inputs like S0, S1 & S2, and eight outputs like O0, O1, O2, O3, O4, O5,O6 and O7. In addition to its 3 select input lines & 8 output lines, this type of Demux is also known as 3:8 Demux. A data distributor is another term for this device.

1 x 8 Demultiplexer

The Truth Table of the 1×8 multiplexer is given below:

S2

S1

S0

O7

O6

O5

O4

O3

O2

O1

O0

0

0

0

0

0

0

0

0

0

0

I

0

0

1

0

0

0

0

0

0

I

0

0

1

0

0

0

0

0

0

I

0

0

0

1

1

0

0

0

0

I

0

0

0

1

0

0

0

0

0

I

0

0

0

0

1

0

1

0

0

I

0

0

0

0

0

1

1

0

0

I

0

0

0

0

0

0

1

1

1

I

0

0

0

0

0

0

0

Depending on which input combination is selected, it sends one input line to one of the eight output lines, such as input line 'I' is connected to one of the outputs from O0 to O7 based on the S0, S1 & S2 select lines.

The Boolean function can be determined using the truth table.

O0 = S2’ S1’ S0’ I
O1 = S2’ S1’ S0 I
O2 = S2’ S1 S0’ I
O3 = S2’ S1 S0 I
O4 = S2 S1’ S0’ I
O5 = S2 S1’ S0 I
O6 = S2 S1 S0’ I
O7 = S2 S1 S0 I

 

The Circuit Diagram of 1 x 8 multiplexer can be designed through 8 AND logic gates & 3 NOT logic gates.

1 x 16 Demultiplexers

A 1x16 demultiplexer can be implemented with the help of a 1x8 demultiplexer and a 1x2 demultiplexer. There is one input, four selection lines, and sixteen outputs on a 1x16 De-Multiplexer. Based on the four select lines, it transmits the signal from a single input line to a single output line from O0 to O15.

1 x 16 Demultiplexers

We can write the Boolean function for the output (O) as

O0= S0′.S1′.S2′.S3′ I
O1= S0′.S1′.S2′.S3 I
O2=.S0′.S1′.S2.S3′ I
O3= S0′.S1′.S2.S3 I
O4= S0′.S1.S2′.S3′ I
O5= S0′.S1.S2′.S3 I
O6= S0′.S1.S2.S3′ I
O7= S0′.S1.S2.S3 I
O8 = S0.S1′.S2′.S3′ I
O9 = S0.S1′.S2′.S3 I
O10 = S0.S1′.S2.S3′ I
O11= S0.S1′.S2.S3 I
O12 = S0.S1.S2′.S3′ I
O13= S0.S1.S2′.S3 I
O14= S0.S1.S2.S3′ I
O15= S0.S1.S2′.S3 I

 

The Circuit Diagram of 1x16 Multiplexer

It can be constructed by 16 AND logic gates, and 4 NOT logic gates are required. Various select line combinations within a given time can enable one AND logic gate so that the input data appears as the output.

Applications of Demultiplexer

Some of the applications of demultiplexer are:

  • Mux’s and demuxes are both used for data transmission.
     
  • Demultiplexers convert the output of multiplexers into their original forms at the receiver end.
     
  • Inputs from the ALU are fed to the demultiplexer. This allows multiple registers to be stored in the output of the ALU.
     
  • Parallel data can be reconstructed using this converter.

Advantages of Demultiplexer

Here are some of the advantages of a demultiplexer.

  • Demultiplexers separate back mutual signals into separate streams.
     
  • Demultiplexers have the opposite function from multiplexers. 
     
  • It can be used in Security systems that can use them as a decoder.
     
  • To transmit audio or video signals, Mux & Demux are used.
     
  • Demultiplexers and Multiplexers in combination are used to improve communication systems. 

Disadvantages of Demultiplexer

Let us look at some of the disadvantages of demultiplexers.

  • There can be a loss of bandwidth with the use of a demultiplexer.
     
  • As a result of the synchronization of signals, delays can occur.

Frequently Asked Questions

What is the main function of a demultiplexer?

The main function of a demultiplexer is to generate multiple outputs for data and signals. It processes digital data and information by collecting them from several sources and integrating them into a single source as the output.

What is a 1 2 demultiplexer?

The 1: 2 demultiplexer comprises of 1 input line(l), 1 select line(S), and 2 output lines (Y0 and Y1). The output line to which the input data will be sent to determined by the logic level that is applied at the select line.

What is demux with example?

Demux is also known as a demultiplexer. demux is defined as a circuit that can deliver multiple outputs from a single input. A demux can perform as a single input with multiple output switches. For example, for 1 input there are 4 outputs; for 1 input, there are 8 outputs.

What is a 2 4 demultiplexer?

A 2 4 demultiplexer has two select lines and 4 output lines. which means the input data goes to any one of the four outputs at a given time for a specific combination of select lines.

Which IC is used for demultiplexer?

The 74LS138 or 74HC138 is commonly used as a demultiplexer IC. It's a 3-to-8 line demultiplexer, capable of selecting one of eight data lines and routing it to a single output line based on the input selection. It's widely used in digital electronics for data routing applications.

Conclusion

This article provides an overview of Demultiplexers. Demuxers, demultiplexers, and data distributors transmit several outputs from a single input. Here, a single input is shared among multiple outputs.

There are several types of demultiplexers, such as 1x2, 1x4, 1x8, and 1x16. Their logic circuits are also discussed and some important applications of demultiplexers.

We recommend that you take a look at the web development guided path if you're interested in learning more.

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