Combinational Logic circuits

Which of the following logic expressions represents the logic diagram shown?

• X=AB’+A’B

• X=(AB)’+AB

• X=(AB)’+A’B’

• X=A’B’+AB

The device shown here is most likely a ________

• Comparator

• Multiplexer

• Demultiplexer

• Inverter

3 bits full adder contains ________

• 3 combinational inputs

• 4 combinational inputs

• 6 combinational inputs

• 8 combinational inputs

What is a multiplexer?

• It is a type of decoder which decodes several inputs and gives one output

• A multiplexer is a device which converts many signals into one

• It takes one input and results into many output

• It is a type of encoder which decodes several inputs and gives one output

In a multiplexer, the selection of a particular input line is controlled by ___________

• Data controller

• Selection Lines

• Logic Gates

• None of above

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

• 2

• m

• n

• 2n

How many select lines would be required for an 8-line-to-1-line multiplexer?

• 2

• 4

• 8

• 3

How many NOT gates are required for the construction of a 4-to-1 multiplexer?

• 3

• 2

• 5

• 4

Answer explanation

Not gate are added for selection lines. 4:1 multiplexer requires 2 selection lines, each will have one NOT gate.

So answer is 2.

A combinational circuit is one in which the output depends on the ____________

• Input combination at the time

• Input combination and the previous output

• Input combination at that time and the previous input combination

• None of above

Most demultiplexers facilitate which type of conversion?

• Decimal to hexadecimal

• Single input multiple output

• AC to DC

• Odd parity to even parity