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Demultiplexers and Their Applications
What is a Demultiplexer?
A demultiplexer is a combinational logic circuit that accepts a single input and distributes it over several output lines. Demultiplexer is also termed as DEMUX in short. As demultiplexer is used to transmit the same data to different destinations, hence it is also known as data distributor.
There is another combinational logic circuit named multiplexer which performs opposite operation of the demultiplexer, i.e. accepts several inputs and transmits one of them at time to the output line.
From the definition, we can state that a demultiplexer is a 1-to-2n device. The functional block diagram of a typical 1:2n demultiplexer is shown in Figure-1.
It can be seen that the demultiplexer has only one data input line, 2n output lines, and n select lines. The logic level applied to select lines of the demultiplexer determines the output channel to which the input data will be transmitted.
Demultiplexer circuit are the combinational logic circuit widely used in digital decoders and Boolean function generator circuits.
Types of Demultiplexers
Based on the number of output lines (2n), demultiplexers can be classified into several types. Some commonly used types of demultiplexers are −
Now, let us briefly discuss each type of demultiplexer.
The functional block diagram of a 1:2 demultiplexer is shown in Figure-2.
The 1:2 demultiplexer consists of 1 input line (I), 1 select line (S), and 2 output lines (Y0 and Y1). The logic level applied at the select line determines the output line to which the input data will be transmitted.
The operation of the 1:2 demultiplexer can be analyzed with the help of its function table given below.
From this function table of 1:2 demultiplexer, we can directly derive the Boolean expression for each output as follow.
The functional block diagram of 1:4 demultiplexer is shown in Figure-3.
The 1:4 demultiplexer has 1 input line (I), 2 select line (S0 and S1), and 4 output lines (Y0, Y1, Y2, and Y3). The logic level applied to the select lines determines the output line to which the input data (I) will be transmitted.
The operation of the 1:4 demultiplexer can be understood with the help of its function table given below.
From this truth table of 1:4 demultiplexer, we can directly write the Boolean expression for each output as follow.
The functional block diagram of 1:8 demultiplexer is shown in Figure-4.
The 1:8 demultiplexer has 1 input line (I), 3 select line (S0, S1, and S2), and 8 output lines (Y0, Y1, Y2, Y3, Y4, Y5, Y6, and Y7). The logic level applied to the select lines will determine the output line to which the input data (I) will be transmitted.
The operation of this 1:8 demultiplexer can be understood with the help of its function table given below.
Using the above function table of 1:8 demultiplexer, we can write the Boolean expression for each output as follow.
Integrated Circuits (ICs) Working as Demultiplexer
Demultiplexers can also be built in the form of ICs. There are several types of ICs available that work as demultiplexer. Some common of them are listed below −
74139 IC works as a 1:4 Demultiplexer
74237 IC works as a 1:8 Demultiplexer
74154 IC works as a 1:16 Demultiplexer
Advantages of Demultiplexers
The important advantages of demultiplexers are given below −
By using demultiplexers, we can increase the efficiency of the communication systems.
Demultiplexer can separate different signals from a mixed signal stream.
Demultiplexer can decode the signals produced by a multiplexer.
Disadvantages of Demultiplexers
The major disadvantages of demultiplexers are listed below −
The use of demultiplexer can cause wastage of bandwidth.
The synchronization of signals can create a delay in the system.
Applications of Demultiplexers
Demultiplexer is a crucial combinational logic circuit which is used in a number of applications. Some important uses of demultiplexers are listed below −
Demultiplexers are used in several input and output devices for data routing.
Demultiplexers are used in digital control systems to select one signal from a mutual stream of signals.
Demultiplexers are also employed for data transmission in synchronous systems.
Demultiplexers are also utilized in data acquisition systems.
Demultiplexers can be used for generating Boolean functions.
Demultiplexers can be used in serial to parallel converters.
Demultiplexers are used for broadcasting of ATM packets.
Demultiplexers can also be used to design automatic test equipment, etc.
This is all about demultiplexer, its types, and applications.
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