Demultiplexers (DeMUX) in Digital Logic: Routing Signals to Multiple Outputs
Learn about demultiplexers (demux or DeMUX), combinational logic circuits that route a single input signal to one of several output lines. This guide explains their functionality, using a 1x4 demultiplexer as an example, and shows how selection lines control signal routing.
De-Multiplexers in Digital Logic
What is a De-Multiplexer?
A demultiplexer (demux or DeMUX) is a combinational logic circuit that routes a single input signal to one of several output lines. Think of it as a switch that directs traffic; it selects which output line receives the input signal based on the selection lines. It's the opposite of a multiplexer (MUX).
De-Multiplexer Structure
A demultiplexer has one data input line, n selection lines, and 2n output lines. The selection lines determine which output line receives the input signal.
1x4 De-Multiplexer
(A block diagram of a 1x4 demultiplexer should be included here. The single input line, two selection lines (S₁, S₀), and four output lines (y₃, y₂, y₁, y₀) should be clearly labeled.)
Truth Table for a 1x4 De-Multiplexer
| S₁ | S₀ | y₃ | y₂ | y₁ | y₀ |
|---|---|---|---|---|---|
| 0 | 0 | 0 | 0 | 0 | I |
| 0 | 1 | 0 | 0 | I | 0 |
| 1 | 0 | 0 | I | 0 | 0 |
| 1 | 1 | I | 0 | 0 | 0 |
(Where I is the input signal.)
Boolean Expressions for a 1x4 De-Multiplexer
Based on the truth table, we can derive the Boolean expressions for each output:
- y₃ = S₁S₀I
- y₂ = S₁S₀'I
- y₁ = S₁'S₀I
- y₀ = S₁'S₀'I
Building Larger De-Multiplexers
Larger demultiplexers can be constructed using smaller ones. For example, a 1x8 demultiplexer can be built using a 1x2 demultiplexer followed by two 1x4 demultiplexers.
1x8 De-Multiplexer
(A block diagram of a 1x8 demultiplexer constructed from a 1x2 and two 1x4 demultiplexers should be included here. The single input line, three selection lines (S₂, S₁, S₀), and eight output lines (y₇, y₆, y₅, y₄, y₃, y₂, y₁, y₀) should be clearly labeled. The truth table for a 1x8 demultiplexer should also be included here.)
Conclusion
Demultiplexers are essential components in digital systems for routing data to specific destinations. Understanding their functionality and how to build larger demultiplexers from smaller ones is a key aspect of digital logic design.