Difference between Decoder and Demultiplexer

Decoders and Demultiplexers both are digital logic components used in electronic circuits to perform specific tasks related to signal routing and control. While they might seem similar at first glance, they serve different purposes and have distinct characteristics. Here’s an explanation of the key differences between a decoder and a demultiplexer.

Decoder

This Decoder is a combinational logic circuit, and its purpose is to decode the data given to it. It is made of n number of input lines and 2*n output lines. For every probable input condition, there are various output signals and depending on the input, only one output signal will produce the logic. So, this n-to-2n decoder is also called a min-term generator, where each output outcomes only at a particular input.

Need of Decoder

• Memory Addressing: In computer systems, decoders are used to interpret memory addresses. They take a binary address as input and activate the specific memory location corresponding to that address. This allows the computer to read or write data to the right location in memory.

• Seven-Segment Displays: Decoders are often used to drive seven-segment displays, which are commonly seen in digital clocks and calculators. Each segment represents a digit, and the decoder translates a binary input into the correct combination of segments to display the desired digit.

• Control Systems: Decoders play a role in control systems, where they interpret input signals to trigger specific actions. For example, in an automated factory, a decoder might interpret signals from sensors to control the movement of robotic arms or conveyor belts.

Demultiplexer

This Demultiplexer is kind of the same as the decoder, but it contains select lines as well. It is used to send the single input over the multiple output lines. It accepts data from one input signal and transfers it over the provided number of output lines. It contains data input lines, select lines and output lines.

Need of Demultiplexer

• Data Distribution: Demultiplexers are used to distribute data from one source to multiple destinations. For instance, in telecommunications, a demultiplexer can separate different channels of data from a single input stream so that each channel can be processed separately.

• Address Decoding: In microprocessors, demultiplexers can be used for address decoding. They take a portion of an address and select a specific memory or peripheral device based on that address, ensuring that the right data gets to the right place.

• Multiplexed Displays: Demultiplexers are often used to drive multiplexed displays, where multiple LEDs or segments share a common set of connections. The demultiplexer selects which individual display to activate at a given time, creating the illusion of multiple active displays.

• Analog to Digital Conversion: Demultiplexers can be used in analog-to-digital converters to select different input channels for conversion. This is particularly useful when you have multiple analog signals that need to be digitized one at a time.

Difference Between Decoder and Multiplexer

Comparison	Decoder	Demultiplexer
Basic	These are Logic circuit which decodes an encrypted input stream from one to another format.	It is a Combination circuit which routes a single input signal to one of several output signals.
Input/Output	n number of input lines and 2n number of output lines.	n number of select lines and 2n number of output lines.
Inverse of	Encoder.	Multiplexer.
Application	In Detection of bits, data encoding.	In Distribution of the data, switching.
Use	It is used for changing the format of the instruction in the machine specific language.	It is used as a routing device to route the data coming from one signal into multiple signals.
Select Lines	Not contains.	Contains.
Implementation	Majorly implemented in the networking application.	Employed in data-intensive applications where data need to be changed into another form.

Decoder vs Demultiplexer – FAQ’s

Q.1: How does a Decoder work?

Answer:

A decoder operates by activating a specific output line that corresponds to the binary value represented by its input lines. For example, in a 2-to-4 decoder, two input lines represent the binary value (00, 01, 10, or 11), and one of the four output lines is activated based on the input combination.

Q.2: How does a Demultiplexer work?

Answer:

A demultiplexer directs the input signal to one of its output lines based on the value of the selection line. If there are ‘n’ output lines, the demultiplexer has a ‘log2(n)’ bit selection input. The input signal is then directed to the output line corresponding to the binary value of the selection input.

Q.3: Can a Demultiplexer be built using Decoders?

Answer:

Yes, a demultiplexer can be constructed using multiple decoders. By connecting the outputs of the decoders to the appropriate output lines of the demultiplexer and using the selection input to enable one of the decoders, you can achieve demultiplexing functionality.