MULTIPLXERS
A Multiplexer (MUX) can be described as a combinational circuit that receives binary
information from one of the 2^n input data lines and directs it to a single output line.
The selection of a particular input data line for the output is decided on the basis of
selection lines.
The multiplexer is often called as data selector since it selects only one of many data
inputs.
Multiplexers are used in various applications wherein multiple-data need to be
transmitted by using a single line.






Communication System. ...
Computer Memory. ...
Telephone Network. ...
Transmission from the Computer System of a Satellite. ...
Communication System. ...
Arithmetic Logic Unit. ...
Note: A 2^n-to-1 multiplexer has 2^n input data lines and n input selection lines whose bit
combinations determine which input data are selected for the output.
The following image shows the block diagram of a 4 * 1 Multiplexer.
Out of these four input data lines, a particular input data line will be connected to the
output based on the combination of inputs present at these two selection lines.
Note: A truth table describing the circuit needs 64 rows since six input variables can have
2^n binary combinations. This will result in an excessively long table. Therefore, a more
convenient way to describe the operation of multiplexers is using a function table.
The function table for a 4 * 1 Multiplexer can be represented as:
S1
S0
y
0
0
I0
0
1
I1
1
0
I2
1
1
13
From the function table, we can write the Boolean function for the output (y) as:
y = S1'S0'I0 + S1' S0'I1 + S1S0'I2 + S1S0I3
y = S1'S0'I0 + S1' S0'I1 + S1S0'I2 + S1S0I3
MCQ’S ON ENCODERS/DECODERS/MULTIPLXERS
1)
2)
3)
4)
5)
6)
7)
A logic circuit that converts a number from any base to binary is known as
Octal to binary encoder is also called as –
In octal to binary encoder how many input lines are there?
The highest octal digit seven has binary value___________________
The binary output in octal to binary has how many bits???
How many OR gates are used to provide outputs in octal to binary encoder
11)
12)
How many output lines are used in hexadecimal to binary encoder
Identify the logic circuit given below
a combinational circuit that produces reverse operation of decoder
8) Process of converting from any type to binary form is called as_________
9) An encoder consists of________input lines n output lines
10) To determine the output lines_______>=I
13) a combinational circuit that converts binary numbers to number of any base
14) Decoder converts ________ input lines to a maximum of _____ unique output
15)
16)
A
0
0
0
0
1
1
1
1
lines
The decoder which converts a binary number to its ________ equivalent number is
known as 3X8 decoder.
Identify for which circuit, this truth table is used.
B
0
0
1
1
0
0
1
1
C
0
1
0
1
0
1
0
1
D0
1
0
0
0
0
0
0
0
D1
0
1
0
0
0
0
0
0
D2
0
0
1
0
0
0
0
0
D3
0
0
0
1
0
0
0
0
D4
0
0
0
0
1
0
0
0
D5
0
0
0
0
0
1
0
0
D6
0
0
0
0
0
0
1
0
D7
0
0
0
0
0
0
0
1
17) How many not gates are used in 3x8 decoder
18) How many AND gates are used in 3X8 decoder.
19)
Identify the circuit.
20 Truthtablefor_____________ TO __________, ____________
Decimal
F3
F2
F1
F0
Number
0
0
0
0
0
1
0
0
0
1
2
0
0
1
0
3
0
0
1
1
4
0
1
0
0
5
0
1
0
1
6
0
1
1
0
7
0
1
1
1
8
1
0
0
0
9
1
0
0
1
20)
Identify the circuit given below
22) A Multiplexer is used in numerous applications like, where multiple datacanbe transmittedusing
a__________________ line
23) Multiplexer is a combinational circuit that has maximum of ______datainputs,_____selectionlinesand
_________outputline.
24) Multiplexer is also called as a _________________
25)
Multiplexersarealsoknownas____________