Decoder is also a Combinational circuit which transforms given inputs to a maximum number of outputs (maximum outputs equal to 2ⁿ and n are given inputs ).

In other words, a decoder can be defined as a logic circuit that receives binary input and produces output corresponding to that very binary input.

A block diagram of decoder consists of n input lines, one or more enable inputs and 2ⁿ maximum number of output lines.

To construct a decoder, we require to know the number of all possible output lines that totally depends on the given input.

So, if n represents given input lines then possible output lines would be 2ⁿ.
Decoder with three inputs would give 8 outputs (n=2,2³ that is 8).

In this article, we’ll be going to design 3 to 8 decoder step by step.

Here are the steps to Construct 3 to 8 Decoder

Step 1. Now we know possible outputs for 3 inputs, so construct 3 to 8 decoder, having 3 input lines, a enable input and 8 output lines.

In the below diagram, given input represented as I2, I1 and I0 , all possible outputs named as  O_0, O_1, O_2,O_3, O_4, O_5,O_6 & O₇ and a E were represented by Enable input.

With Enable input

Just as Multiplexer, Decoder is also a Combinational circuit  which transforms given inputs to maximum number of outputs(maximum outputs equal to 2ⁿ and n are given inputs ).
A block diagram of decoder consists input lines, one or more enable inputs and maximum number of output lines.
To construct a decoder, we require to know the number of all possible output lines that totally depends on the given input.
So, if  n represents given input lines then possible output lines would be 2ⁿ .
Decoder with two inputs would give 4 outputs (n=2,2² that is 4).

Step 1. Now we know possible outputs for 2 inputs, so construct 2 to 4 decoder , having 2 input lines, a enable input and 4 output lines. In the below diagram, given input represented as I1 and I0 , all possible outputs named as  O_0, O_1, O_{2, &} O₃ and a E were represented by Enable input.

With Enable input