Multiplexers - GATE CSE (CSE) Digital Logic Free MCQ Test with solutions

Multiplexer:

• A multiplexer (MUX) is a combinational logic circuit designed to switch one of several inputs to a single common output line.
• A multiplexer is Many to One data selector
• A multiplexer selects one of the many data available at its input depending on the bits on the select line
• For 2n inputs, there are n select lines that determine, which input is to be connected to the output.

Example:
A 4-input multiplexer is as shown below.

 

Output, Y = I₀S̅₁S̅₀ + I₁S̅₁S₀ + I₂S₁S̅₀ + I₃S₁S₀

The output of 4-input multiplexer represents one combinational functions of 3-variables each.

Multiplexer:

• It is a combinational circuit that converts multiple inputs into a single output, depending upon the status of the selection lines.
• For n selection lines, 2n inputs are available in a multiplexer.
• Depending upon the status of the selection lines, one input is the selected output of 2n inputs and converted into the output.

​Explanation:

• For n selection lines, 2n AND gates are required in a multiplexer.
• For the implementation of 1-to-8 multiplexer, 8 AND gates are required.
  

Concept:

    For selecting eight inputs, there are three data select lines that must be used. The multiplexer requires the data select lines. We have three data select lines for eight inputs, and it's an 8:1 multiplexer.

Hence the correct answer is 3.

Concept:

In a 4 × 1 MUX

Truth-Table is given as:

Y = Output = S̅₁ S̅₀ I₀ + S̅₁ S₀ I₁ + S₁ S̅₀ I₂ + S₁ S₀ I₃
MUX contains AND gate followed by OR gate
Calculation:
Given:

Z = Output = A̅B̅C + A̅BC + AB̅C̅ + ABC̅ 
Z = A̅C(B̅ + B) + AC̅(B̅ + B)
Z = A̅C + AC̅
Z = A XOR C
Hence, option 4 is correct.

A multiplexer (or MUX) is a device that selects one of several analog or digital input signals and forwards the selected input into a single line, depending on the active select lines.

It is possible for an enable or strobe input to undergo an expansion of two or more MUX ICs to the digital multiplexer with the proficiency of large number of inputs.

Enable input is used to active the chip, when enable is high the chip works (ACTIVE), when enable is low the chip does not work (MEMORY). However, Enable can be Active-High or Active-Low, indicating it is active either when it is connected to VCC or GND respectively.

A digital multiplexer is a combinational circuit that selects one digital information from several sources and transmits the selected information on a single output line depending on the status of the select lines. That is why it is also known as a data selector.

If the number of n selected input lines is equal to 2^m then it requires m select lines to select one of m select lines.

Data Selector is another name of Multiplexer. A multiplexer (or MUX) is a device that selects one of several analog or digital input signals and forwards the selected input into a single line, depending on the active select lines.