Decoder in Digital Electronics

Last Updated on December 26, 2023 by Ankit Kochar

In the realm of digital electronics, decoders stand as fundamental components that play a pivotal role in transforming coded information into a more understandable format. Decoders are essential in various applications, translating binary data into specific outputs, enabling efficient communication between different parts of electronic systems. Their significance spans across numerous fields, from computer architecture and telecommunications to everyday consumer devices. Understanding the functionality and significance of decoders is key to comprehending their widespread application in modern technology.

Decoder in Digital Electronics

Decoder in Digital Electronics is defined as a combinational circuit that converts the N inputs into 2N Outputs. In simple terminology, it is just the opposite of an encoder, which converts the 2N inputs to N Outputs. The 2N output lines of the decoder correspond to some binary information. The block diagram of a general decoder is given below for a better understanding of the above-mentioned statements.

Various Types of Decoder in Digital Electronics that are commonly used are given below:

2 to 4 Decoder in Digital Electronics

A 2 to 4 Decoder in Digital Electronics is the combinational circuit that converts the 2-bit binary information into 4-bit binary information on basis of Enable signal.

Inputs: A0, A1, E
Output: Y0, Y1, Y2, Y3

Block Diagram of 2 to 4 Decoder in Digital Electronics

Here is the block diagram representing the 2 to 4 Decoder in Digital Electronics.

Truth Table of 2 to 4 Decoder in Digital Electronics

When the Enable Signal (E) is 1, one of the outputs is 1 and the rest corresponds to 0. Here is the Truth Table for 2 to 4 Decoder in Digital Electronics.

From the above truth table, we can write the logical expressions for the output terms as

Y3 = E.A1.A0
Y2 = E.A1.A0'
Y1 = E.A1'.A0
Y0 = E.A1'.A0'

Logic Circuit of 2 to 4 Decoder in Digital Electronics

From the above logical expressions, the logical circuit diagram is constructed as.

3 to 8 Decoder in Digital Electronics

The 3 to 8 Decoder in Digital Electronics is responsible for converting 3-bit data to 8-bit data. It can be better understood by keeping in mind, that from 3 bits of data, maximum 8 numbers of combinations are possible.

Input: A0, A1, A2
Output: Y0, Y1, Y2, Y3, Y4, Y5, Y6, Y7

Block Diagram of 3 to 8 Decoder in Digital Electronics

The block diagram of 3 to 8 Decoder in Digital Electronics with 3 input lines and 8 Output lines is given below.

Truth Table of 3 to 8 Decoder in Digital Electronics

Here is the Truth Table for this combinational Circuit.

The logical expressions for output signals can be deduced from the above truth table are

Y0 = A0'.A1'.A2'
Y1 = A0.A1'.A2'
Y2 = A0'.A1.A2'
Y3 = A0.A1.A2'
Y4 = A0'.A1'.A2
Y5 = A0.A1'.A2
Y6 = A0'.A1.A2
Y7 = A0.A1.A2

Logic Circuit of 3 to 8 Decoder in Digital Electronics

Here is the logic circuit drawn with the help of NOT and AND Logic Gates.

4 to 16 Decoder in Digital Electronics

Now since the maximum number of combinations possible from 4 bits is 16. So, the 4 to 16 Decoder in Digital Electronics converts 4-bit input data into 16-bit Output binary information.

This 4 to 16 Decoder is constructed using two 3 to 8 Decoders.

Inputs: A0, A1, A2
Outputs: Y0, Y1, Y2, Y3, Y4, Y5, Y6, Y7 Y8, Y9, Y10, Y11, Y12, Y13, Y14, Y15

Block Diagram of 4 to 16 Decoder in Digital Electronics

The block diagram of 4 to 16 Decoder in Digital Electronics using two 3 to 8 Decoders is given below.

Truth Table of 4 to 16 Decoder in Digital Electronics

Here is the truth table with all possible inputs and outputs.

Logical Expressions for output can be deduced as:

Y0 = A0'.A1'.A2'.A3'
Y1 = A0'.A1'.A2'.A3
Y2 = A0'.A1'.A2.A3'
Y3 = A0'.A1'.A2.A3
Y4 = A0'.A1.A2'.A3'
Y5 = A0'.A1.A2'.A3
Y6 = A0'.A1.A2.A3'
Y7 = A0'.A1.A2.A3
Y8 = A0.A1'.A2'.A3'
Y9 = A0.A1'.A2'.A3
Y10 = A0.A1'.A2.A3'
Y11 = A0.A1'.A2.A3
Y12 = A0.A1.A2'.A3'
Y13 = A0.A1.A2'.A3
Y14 = A0.A1.A2.A3'
Y15 = A0.A1.A2'.A3

Logic Circuit of 4 to 16 Decoder in Digital Electronics

The logic circuit as per Truth Table and Logical Expressions is given below.

Applications of Decoder in Digital Electronics

Decoders are used in various digital systems, such as microprocessors, memory units, and various other digital circuits. Here are some of the common applications of decoders:

• Memory Units: Decoders in Digital Electronics are commonly found in memory units like RAM and ROM. A decoder is required by a memory unit to pick a specific memory address for read or write operations. The decoder provides a unique output signal that is used to access a particular memory address.
• Microprocessors: Decoders are used by microprocessors to decode the instruction set. The decoder provides a unique output signal that is used to carry out the instruction. Decoders are also used by the microprocessor to decode addresses and data bus signals.
• Digital Clocks: BCD decoders are used in digital clocks to transform binary-coded decimal codes into decimal codes that indicate hours, minutes, and seconds. For each decimal digit, the BCD decoder outputs a distinct output signal.
• Audio and Video Decoders: Decoders convert digital audio and video information into analog signals that may be played on a speaker or display device. The decoder generates a unique output signal that is used to reconstruct the analog signal.

Conclusion
In conclusion, decoders form an integral part of digital electronics, serving as vital components that facilitate the conversion of encoded information into meaningful outputs. Their versatility and applicability across diverse industries underscore their importance in enabling efficient communication and data processing within electronic systems. As technology continues to advance, the evolution of decoders is expected to further refine their capabilities, contributing to the enhancement of various electronic devices and systems.

Frequently Asked Questions (FAQs) Related to Decoder in Digital Electronics

Here are some Frequently Asked Questions on Decoder in Digital Electronics.

1. What is the function of a binary decoder?
A binary decoder is used to convert a binary code into a active-low output signal.

2. What are the different types of decoders?
There are various types of decoders, including binary decoders, priority decoders, BCD (Binary-Coded Decimal) decoders, and multiplexers acting as decoders. Each type serves specific purposes, such as converting binary inputs into different formats or selecting a particular output based on priority.

3. Where are decoders used in everyday technology?
Decoders find applications in numerous everyday devices and systems. They are commonly used in remote controls, memory systems, digital displays, address decoding in computer systems, communication systems, and more. Their ability to decode and activate specific outputs based on input data makes them crucial in enabling functionality in various electronic devices.

4. How do decoders differ from encoders?
Decoders and encoders are opposites in functionality. While decoders convert coded information into a more understandable format, encoders perform the reverse function by converting data from a more understandable format into a coded representation. Encoders encode information, while decoders decode it for interpretation or activation of specific outputs.

5. How are decoders implemented in digital systems?
Decoders can be implemented using various logic gates, such as NAND gates, NOR gates, or AND gates.