Explain Decoder with Truth Table | Circuit Diagram | Logical Expression in Digital electronics

Summary

In this tutorial, the concept of a decoder is introduced as a combinational circuit with multiple input and output lines. The video explains how a decoder works, its block diagram, and the importance of the enable signal. The functioning of a 2-to-4 line decoder is described with its truth table, logical expressions, and circuit diagram. Additionally, the logical diagram and conditions under which outputs are activated are detailed. The tutorial also touches on the generation of outputs for other types of decoders like 3-to-8 and 32-line decoders, providing a comprehensive understanding of decoder circuits.

Takeaways

• 😀 A decoder is a combination circuit with 'n' input lines and '2^n' output lines that generates output based on binary input.
• 😀 The decoder works by converting binary input to a unique output line based on '2^n' possible combinations.
• 😀 The block diagram of a decoder includes 'n' input lines, an enable line, and '2^n' output lines.
• 😀 The enable line controls whether the input lines are active or not; when it is zero, no output is generated.
• 😀 A decoder can generate only one active output at a time; all other outputs remain inactive.
• 😀 The truth table for a decoder shows the input-output relationship, where different inputs correspond to specific outputs.
• 😀 The logical expression for a decoder is based on the combinations of inputs and the enable signal, determining which output is activated.
• 😀 For a 2-line decoder, when the enable signal is active (1), one of the two outputs will be activated based on the input values.
• 😀 A 4-line decoder (2^2 outputs) uses 2 input lines and an enable line to generate 4 output lines with specific input-output mapping.
• 😀 The logical diagram for a decoder is constructed using AND gates based on the required combinations of inputs and the enable signal.
• 😀 A 3-to-8 decoder has 3 input lines, one enable line, and 8 output lines, with each output activated based on the binary input combinations.

Q & A

What is a decoder in digital electronics?

A decoder is a combination circuit that has multiple input lines and generates output lines as a result. It converts binary input into a corresponding binary output.

How does a decoder function with enable signals?

In a decoder, the enable signal determines whether the inputs are active. If the enable is zero, no output is generated, but if it is one, the output will depend on the inputs.

What is the significance of the enable signal in a decoder?

The enable signal is critical as it controls whether the decoder's input will generate any active output. If the enable is zero, no output will be active, but if it is one, the output will change based on the inputs.

Can you explain the basic structure of a 2-to-4 line decoder?

A 2-to-4 decoder has two input lines and four output lines. It also includes an enable line. When the enable is set to one, the decoder generates one active output corresponding to the input combination.

What does the truth table for a 2-to-4 decoder represent?

The truth table for a 2-to-4 decoder shows the relationship between the input and output. It maps each combination of input values to one active output line when the enable is active (one).

How do the inputs affect the output of a 2-to-4 decoder?

For a 2-to-4 decoder, the output will be determined by the binary value of the inputs. Only one output line will be active at any time based on the input combination when the enable signal is active.

What is the logical expression for a 2-to-4 decoder's output?

The logical expression for each output in a 2-to-4 decoder depends on the input values and the enable signal. For example, Y1 is active when the input is A1 bar and A0, and similar expressions can be formed for other outputs.

How is the logical diagram of a 2-to-4 decoder constructed?

In the logical diagram of a 2-to-4 decoder, the input lines (A0 and A1) and the enable line are used with logic gates to produce the correct active output based on the input values.

What happens when the enable signal is set to zero in a decoder?

When the enable signal is set to zero, all output lines in the decoder will remain inactive, regardless of the input values.

How does a 3-to-8 decoder differ from a 2-to-4 decoder?

A 3-to-8 decoder has three input lines, which allow it to generate eight output lines, as opposed to a 2-to-4 decoder that has only four outputs. The structure and logic for the 3-to-8 decoder are similar but with one additional input.