Which is true of a DEMUX tree?

Number of outputs is the product of outputs at each level; delay grows with levels

Number of outputs is the sum of outputs at each level

It needs extra AND gates for every level

2074 Asoj · 3 marks

Short note: DE-MUX tree

Short answer

A DEMUX tree builds a larger demultiplexer by cascading smaller ones in levels. The first level uses higher-order select bits, and lower levels use lower-order bits. No extra gates are needed, but propagation delay increases with levels.

Write a short note on DE-MUX tree.

A DEMUX tree is a large demultiplexer formed by connecting smaller demultiplexers in two or more levels. It is used when a DEMUX of the required size is not available as one IC.

Principle: the first-level DEMUX receives the data input and is driven by the higher-order select bits; each of its outputs feeds a second-level DEMUX driven by the lower-order select bits. Number of outputs = product of the outputs of each level.

Example: 1:16 DEMUX from five 1:4 DEMUXes

                      S1 S0
         S3 S2     +-->[1:4]-- Y0..Y3
       +-------+   |
  D -->|  1:4  |---+-->[1:4]-- Y4..Y7
       | DEMUX |---+
       +-------+   +-->[1:4]-- Y8..Y11
                   |
                   +-->[1:4]-- Y12..Y15

If $S_3S_2S_1S_0 = 0110$ , the first DEMUX sends D to the second DEMUX (group 01), which sends it to its output 2, i.e. $Y_6$ .

Features:

No extra gates are needed; only select lines are shared.
Other sizes: 1:32 from 1:8 and 1:4 (or 1:2), 1:8 from 1:2 DEMUXes, etc.
Delay increases with the number of levels.

✓ Answer checked by Claude Opus 5.5 (high effort)

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