how many select lines are required for a 1-to-8 demultiplexer?
For a 1-to-8 demultiplexer, exactly 3 select lines are required.
This standard digital logic design principle ensures the single input routes
to one of eight outputs.
Why 3 Lines?
A demultiplexer (demux) takes one data input and directs it to 2^n outputs
using n select lines, where each combination activates a unique output.
For 8 outputs, solve 2n=82^n=82n=8, so n=log2(8)=3n=\log_2(8)=3n=log2(8)=3.
Thus, select lines S2, S1, S0 create 000 to 111 binary codes, like S2=0, S1=0,
S0=0 activating output Y0.
Truth Table Basics
Here's how it works in action:
| S2 | S1 | S0 | Active Output |
|---|---|---|---|
| 0 | 0 | 0 | Y0 = Input |
| 0 | 0 | 1 | Y1 = Input |
| 0 | 1 | 0 | Y2 = Input |
| 0 | 1 | 1 | Y3 = Input |
| 1 | 0 | 0 | Y4 = Input |
| 1 | 0 | 1 | Y5 = Input |
| 1 | 1 | 0 | Y6 = Input |
| 1 | 1 | 1 | Y7 = Input |
Real-World Example
Imagine memory addressing: 3 select lines pick one of 8 RAM chips, routing data efficiently—like in older systems or FPGA designs today.
TL;DR: 3 select lines power a 1-to-8 demux.
Information gathered from public forums or data available on the internet and portrayed here.
