Demultiplexers

General concept
- Single data input; n control inputs (called "selects"); 2n outputs
- Connects one of 2n outputs to the single input
- Select inputs "choose" which output is connected to the input
- When used as a decoder, the input is called an “enable” (G)

1:2 Decoder:

Out0 = G ? S’

Out1 = G ? S

2:4 Decoder:

Out0 = G ? S1’ ? S0’

Out1 = G ? S1’ ? S0

Out2 = G ? S1 ? S0’

Out3 = G ? S1 ? S0

3:8 Decoder:

Out0 = G ? S2’ ? S1’ ? S0’

Out1 = G ? S2’ ? S1’ ? S0

Out2 = G ? S2’ ? S1 ? S0’

Out3 = G ? S2’ ? S1 ? S0

Out4 = G ? S2 ? S1’ ? S0’

Out5 = G ? S2 ? S1’ ? S0

Out6 = G ? S2 ? S1 ? S0’

Out7 = G ? S2 ? S1 ? S0

General concept