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Difference between Decoder and Demultiplexer
Both decoder and demultiplexer are types combinational logic circuits used for implementing different types of digital systems. However, the function of a decoder is completely different from that of a demultiplexer. A decoder is a combination logic circuit that decrypts an input data stream from one format to another, whereas a demultiplexer is a combination circuit that routes the data from one input line to any of the multiple output lines.
Read this article to find out more about decoders and demultiplexers and how they are different from each other. Let's start with a basic overview of these two combinational logic circuits.
What is a Decoder?
A Decoder is a combinational circuit that has n input lines and a maximum of {2} ^ {n} output lines. One of these outputs will be Active High based on the combination of inputs present, when the decoder is enabled. That means, the decoder detects a particular code. The outputs of a decoder are nothing but the min terms of input variables (lines), when it is enabled.
There are three types of decoders that are most widely used in electronic systems −
2−to−4 decoder
3−to−8 decoder, and
4−to−16 decoder
What is a Demultiplexer?
A Demultiplexer is also a combinational circuit that performs the reverse operation of Multiplexer. It has single input, n selection lines and maximum of {2} ^ {n} outputs. The input will be connected to one of these outputs based on the values of selection lines. Since there are n selection lines, there will be {2} ^ {n} possible combinations of zeros and ones. So, each combination can select only one output.
Demultiplexers are also called as De−Mux. The structure of a demultiplexer is similar to a decoder, however the demultiplexer has select lines that are not present in the decoder. From the explanation of a demultiplexer, it is clear that the demultiplexer accepts information from one input line and transmits this information over multiple output lines as per the select line command.
Difference between Decoder and Demultiplexer
The following table highlights all the points that differentiate a decoder from a demultiplexer −
| Key | Decoder | Demultiplexer |
|---|---|---|
| Purpose | A decoder decodes an encrypted input signal to multiple output signals from one format to another format. | A demultiplexer routes an input signal to multiple output signals. |
| Input / Output | A decoder has input lines and a maximum of {2} ^ {n} output lines. | A demultiplexer has single input, selection lines and maximum of {2} ^ {n} outputs. |
| Inverse | Decoder's inverse is Encoder. | Demultiplexer's inverse is Multiplexer. |
| Usage | Decoders are used to detect bits, encoding of data. | Demultiplexers are used in switching, data distribution. |
| Select Lines | Decoders have no select lines. | Demultiplexers contain select lines. |
| Application | Decoders are heavily used in networking applications. | Demultiplexers are employed in communication systems. |
Conclusion
From the above discussion, it is clear that decoders are quite different from demultiplexers. The most significant difference between the two is that decoders are used to decrypt the encoded data, whereas demultiplexers are used to transmit a single input stream over multiple output lines.
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