The select lines form a binary number. In a 4:1 MUX, S1S0 = 10 selects D2.
Presets:
DEMUX Size
Input Data
Select Value
Only the selected output line receives the input. All other output lines remain 0.
Presets:
Number of Inputs / Outputs
Selected Channel Index
Display Order
Required select lines = log₂(number of channels). Example: 8 channels need 3 select inputs.
Examples:
Circuit Type
Size
Show
The compact select-line table is usually easier to read. Full logic table grows quickly for larger MUX sizes.
📐 Formula Reference
Select Lines
n = log₂(N) N = number of data inputs or outputs
4:1 MUX Output
Y = D0·S1'·S0' + D1·S1'·S0 + D2·S1·S0' + D3·S1·S0
DEMUX Output
Yk = input data when select = k, otherwise 0
Selected Index
index = binary value of select lines
📋 Quick Reference
MUX Select Lines
2:1 MUX1 select
4:1 MUX2 selects
8:1 MUX3 selects
16:1 MUX4 selects
Common ICs
74HC1518:1 MUX
74HC153dual 4:1
74HC1383-to-8 decoder
74HC1544-to-16
Use Case
MUXmany → one
DEMUXone → many
Select linesaddress
Enable pingate control
📚 Digital Logic Notes
MUX means data selectorA multiplexer takes many inputs and selects only one input to pass to the output.
DEMUX means data distributorA demultiplexer takes one input and sends it to one selected output line.
Select lines act like address bitsFor 8 channels, 3 select bits are needed because 2³ = 8.
MUX can implement Boolean functionsBy wiring data inputs as 0, 1, variables or complements, a MUX can act as a logic-function generator.
What is a MUX DEMUX Calculator?
A MUX DEMUX calculator helps calculate multiplexer output, demultiplexer output lines and select-line combinations. It is useful for digital electronics, logic design, IC selection, truth table checking and exam practice.
How many select lines are needed for a multiplexer?
The number of select lines is log₂(N), where N is the number of input channels. A 4:1 multiplexer needs 2 select lines, an 8:1 multiplexer needs 3 select lines and a 16:1 multiplexer needs 4 select lines.
Multiplexer vs demultiplexer
A multiplexer selects one signal from many inputs and sends it to one output. A demultiplexer takes one input signal and routes it to one selected output. In short: MUX is many-to-one, DEMUX is one-to-many.
How to calculate 4 to 1 MUX output?
For a 4:1 MUX, the select lines S1 and S0 form a 2-bit binary number. If S1S0 = 00, output is D0. If S1S0 = 01, output is D1. If S1S0 = 10, output is D2. If S1S0 = 11, output is D3.
❓ Frequently Asked Questions
A multiplexer, or MUX, is a digital circuit that selects one input from multiple input lines and passes it to a single output line based on select inputs.
A demultiplexer routes one input signal to one of several output lines. It is used in data routing, communication systems, memory addressing and digital control circuits.
A 16 to 1 MUX requires 4 select lines because 2⁴ = 16.
Y = D0·S1'·S0' + D1·S1'·S0 + D2·S1·S0' + D3·S1·S0. This means each input is enabled only for its matching select-line combination.
They are closely related. A decoder activates one output based on binary inputs. A demultiplexer is similar but also has a data input or enable input that is routed to the selected output.
Yes. By connecting MUX data inputs to 0, 1, variables or inverted variables, a multiplexer can implement Boolean expressions.