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What are Encoders and Decoders?

In digital electronic projects, encoders and decoders play a particularly important role, allowing data to be converted from one form to another. They are commonly found in communication systems such as those related to telecommunication and networking, enabling the transfer of data. Similarly, within the digital realm, encoders and decoders transmit data. With this in mind, this blog will cover their use in a diverse set of applications and how they work.

An encoder can be defined as either a device, transducer, or circuit, converting information from one format to another. An encoder’s feedback signal determines its position, count, speed, and direction, and control devices are used to send commands for a particular function within a system. To create a signal in an encoder, one may use mechanical, magnetic, resistance, or optical technologies to do so. A decoder, on the other hand, has a very simple function. It can be defined as a circuit that is used to change code into a set of signals.

Both encoders and decoders are designed with logic gates such as an OR-gate. Additionally, there are different types of encoders and decoders including 4-, 8-, and 16-bit variations, and their respective truth tables rely on the particular encoder chosen by a user. In a 4-bit encoder, only four inputs are allowed, A0, A1, A2, and A3, and they generate two outputs, F0 and F1.

Encoders and decoders are used in an array of applications, allowing for the compression of multiple inputs into a smaller number of outputs. Other types of devices that are used in electronic projects are multiplexers and demultiplexers. Multiplexers are devices that enable multiple input signals and produce a single output signal. In contrast, demultiplexers are digital ICs that are used to transmit binary data from one line to many.

Multiplexers are similar to encoders, but their primary difference is that multiplexers have several data input lines and a single output line. Demultiplexers and decoders also have similar digital circuits, however, demultiplexers have a single input line and utilize multiple lines to determine the output line for data transmission.

Common Types of Encoders and Decoders

A priority encoder is a circuit that compresses a multiple binary input into a small number of outputs. The output generated by the priority encoder is displayed in the binary representation of the original number of the most significant bits. Typically, they are used to control interrupt requests by acting on the highest priority encoder. At one time, two or more inputs can be generated, and then the highest priority takes precedence. Another type of encoder is a 74HC148 8-to-3-line encoder which features eight active low inputs and a three-bit active low binary output. The IC is generally enabled by an active low Enable Input, and active low Enable Output is provided so that several ICs can be connected in a cascade, allowing for the encoding of more inputs.

In digital electronics, a binary decoder is a combination logic circuit that converts the binary integer into the associated pattern of output bits. Moreover, the function of a binary decoder is acquired if the given input combination has occurred. The second type of decoder that will be covered is a 2-to-4-line decoder available in HC and HCT types in a number of versions from different manufacturers. These decoders consist of two binary inputs and four coded outputs.


Encoders and decoders can be found in synchronizing motor speed in industries, wireless transmission of real-time video with night vision capabilities, automatic wireless health monitoring systems, and more, making these circuit devices important for a myriad of applications.

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August 19, 2022
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