Designing of 3-Line to 8-Line Decoder and Demultiplexer

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 A decoder is a combinational logic circuit which is used to change the code right into a set of alerts. It's the reverse course of of an encoder. A decoder circuit takes a number of inputs and offers a number of outputs. A decoder circuit takes binary knowledge of ‘n’ inputs into ‘2^n’ distinctive output. As well as to enter pins, the decoder has a enable pin. This permits the pin when negated, makes the circuit inactive. on this article, we talk about 3 to 8 line Decoder and Multiplexer.

The under is the reality desk for easy 1 to 2 line decoder the place A is the enter and D0 and D1 are the outputs.

1 to 2 Decoder
1 to 2 Decoder

The circuit reveals the 1 to 2 decoder logic.

1 to 2 Decoder Circuit
1 to 2 Decoder Circuit

A demultiplexer is a device that takes a single enter and offers one of the a number of output strains. A demultiplexer takes one single enter knowledge and then selects anybody of the only output strains one after the other. It's the reverse process of a multiplexer. Additionally it is referred to as as a DEMUX or an information distributor. A DEMUX converts the enter serial knowledge line into output parallel knowledge. A DEMUX offers ‘2n’ outputs for ‘n’ choice strains with a single enter.


DEMUX is used when the circuit needs to ship the information sign to one of the various units. A decoder is used to choose amongst many units whereas a demultiplexer is used to ship the sign to many units.

The under is the reality desk for 1 to 2 demultiplexer with “I” as enter knowledge, D0 and D1 are the output knowledge line and A is the choice line.

1 to 2 Demux Truth Table
1 to 2 Demux Reality Desk

The circuit reveals the 1 to 2 demultiplexer schematic.

1 to 2 Demux
1 to 2 Demux

3 Line to 8 Line Decoder

This decoder circuit offers 8 logic outputs for 3 inputs and has a enable pin. The circuit is designed with AND and NAND logic gates. It takes 3 binary inputs and prompts one of the eight outputs. 3 to 8 line decoder circuit can also be referred to as as binary to an octal decoder.

3 to 8 Decoder Block Diagram
3 to 8 Line Decoder Block Diagram

The decoder circuit works solely when the Allow pin (E) is high. S0, S1 and S2 are three totally different inputs and D0, D1, D2, D3. D4. D5. D6. D7 are the eight outputs.

Circuit Diagram

3 to 8 Decoder Circuit
3 to 8 Decoder Circuit

3 to 8 Line Decoder Reality Desk

The under desk offers the reality desk of 3 to 8 line decoder.

S0 S1 S2 E D0 D1 D2 D3 D4 D5 D6 D7
x x x 0 0 0 0 0 0 0 0 0
0 0 0 1 0 0 0 0 0 0 0 1
0 0 1 1 0 0 0 0 0 0 1 0
0 1 0 1 0 0 0 0 0 1 0 0
0 1 1 1 0 0 0 0 1 0 0 0
1 0 0 1 0 0 0 1 0 0 0 0
1 0 1 1 0 0 1 0 0 0 0 0
1 1 0 1 0 1 0 0 0 0 0 0
1 1 1 1 1 0 0 0 0 0 0 0

When the Allow pin (E) is low all of the output pins are low.

1 to 8 Demultiplexer

A 1 line to 8 line demultiplexer has one enter, three choose enter strains and eight output strains. It distributes the one enter knowledge into 8 output strains relying on the chosen enter. Din is the enter knowledge, S0, S1, and S2 are choose inputs and Y0, Y1, Y2, Y3, Y4, Y5, Y6, Y7 are the outputs.

1 to 8 DEMUX
1 to 8 DEMUX

Circuit Diagram

1 to 8 Demux circuit
1 to 8 Demux circuit

3 to 8 Decoder/Demultiplexer

IC 74HC238 is used is used as decoder/ demultiplexer. 3 to 8 line decoder demultiplexer is a combinational circuit that can be utilized as each a decoder and a demultiplexer. IC 74HC238 decodes three binary tackle inputs (A0, A1, A2) into eight outputs (Y0 to Y7). The device additionally has three Allow pins. The identical mixture is used as a demultiplexer.

Pin Configuration

The under is the pin configuration for the IC74HC238 3 to 8 line decoder or demultiplexer. It's a 16 pin DIP.


The logical circuit explains the working of the IC 74HC238.

Options of 74HC238 IC

  • Demultiplexing functionality
  • A number of inputs enable for simple enlargement
  • Perfect for memory chip choose decoding
  • Energetic HIGH mutually unique outputs
  • A number of bundle option

Software of Decoder

  • The Decoders have been utilized in analog to digital conversion in analog decoders.
  • Utilized in digital circuits to convert directions into CPU management alerts.
  • They primarily utilized in logical circuits, knowledge switch.

Functions of Demultiplexer

  • Used to join a single source to a number of locations.
  • The Demux is utilized in communication programs to carry a number of knowledge alerts right into a single transmission line.
  • Utilized in Arithmetic Logic Models
  • Utilized in serial to parallel converters in knowledge communications.

Due to this fact, that is the fundamental details about 3 to 8 line decoder and demultiplexers. Hope you might need obtained some elementary ideas about this matter by observing the digital logic circuits and reality tables and their functions. Moreover, any doubts concerning this text or Latest electronics projects, You may write your views about this matter within the remark part under.