# 19 Lecture

## DEMULTIPLEXER

A demultiplexer, or demux for short, is a digital logic circuit that takes one input signal and routes it to one of several possible output lines based on the value of a set of control signals. Essentially, it is the opposite of a multiplexer, w

## Important Mcq's Midterm & Finalterm Prepration Past papers included

1. What is the purpose of a demultiplexer?
2. a) To route one input to several outputs b) To route several inputs to one output c) To combine multiple signals into one output d) None of the above

Solution: a

1. How many control lines are required for a 4-to-1 demultiplexer? a) 1 b) 2 c) 3 d) 4

Solution: b

1. Which logic gate is commonly used to implement a demultiplexer? a) AND gate b) OR gate c) NOT gate d) XOR gate

Solution: a

1. What is the output of a demultiplexer when all control lines are low? a) All outputs are low b) All outputs are high c) One output is high and the rest are low d) None of the above

Solution: a

1. Which demultiplexer is commonly used for decoding address lines in memory devices? a) 1-to-2 demultiplexer b) 2-to-4 demultiplexer c) 3-to-8 demultiplexer d) 4-to-16 demultiplexer

Solution: c

1. Which demultiplexer is equivalent to two 2-to-1 demultiplexers? a) 1-to-2 demultiplexer b) 2-to-4 demultiplexer c) 3-to-8 demultiplexer d) 4-to-16 demultiplexer

Solution: b

1. What is the function of the enable input in a demultiplexer? a) To select which output to route the input to b) To enable or disable the demultiplexer c) To control the polarity of the output signals d) None of the above

Solution: b

1. Which demultiplexer is commonly used for separating the color signals in a video signal? a) 1-to-2 demultiplexer b) 2-to-4 demultiplexer c) 3-to-8 demultiplexer d) 4-to-16 demultiplexer

Solution: a

1. What is the difference between a demultiplexer and a decoder? a) A decoder has multiple inputs and one output, while a demultiplexer has one input and multiple outputs b) A decoder is used for data compression, while a demultiplexer is used for data expansion c) A decoder outputs binary codes, while a demultiplexer outputs analog signals d) There is no difference between a demultiplexer and a decoder

Solution: a

1. Which demultiplexer is commonly used for splitting a serial data stream into parallel data streams? a) 1-to-2 demultiplexer b) 2-to-4 demultiplexer c) 3-to-8 demultiplexer d) 4-to-16 demultiplexer

Solution: a

## Subjective Short Notes Midterm & Finalterm Prepration Past papers included

1. How does a demultiplexer differ from a decoder?

Answer: A demultiplexer has one input and multiple outputs, while a decoder has multiple inputs and one output. A demultiplexer is used to route one input signal to multiple output lines, while a decoder is used to convert a binary code to a corresponding output signal

2. How many output lines does a 2-to-4 demultiplexer have?

Answer: A 2-to-4 demultiplexer has four output lines.

3. What is the function of the enable input in a demultiplexer?

Answer: The enable input is used to enable or disable the demultiplexer. When the enable input is low, the demultiplexer is disabled and all output lines are low.

4. What is the difference between a demultiplexer and a multiplexer?

Answer: A demultiplexer routes one input signal to multiple output lines, while a multiplexer routes multiple input signals to one output line.

5. What is the advantage of using a demultiplexer in a digital communication system?

Answer: A demultiplexer can be used to separate a high-speed data stream into multiple lower-speed data streams, which can be processed by different devices or components.

6. What is the function of the control lines in a demultiplexer?

Answer: The control lines are used to select which output line the input signal is routed to.

7. How is a demultiplexer implemented using basic logic gates?

Answer: A demultiplexer can be implemented using AND gates and NOT gates. The control lines are used to enable the corresponding AND gates, which produce a high output when the input signal matches the desired output line

.

8. What is the output of a demultiplexer when all control lines are high?

Answer: The output of a demultiplexer is undefined when all control lines are high.

9. How does a demultiplexer help in reducing signal interference in a communication system?

Answer: A demultiplexer can separate different signals in a communication system, which helps to reduce signal interference and improve signal quality.

10. How can a demultiplexer be used for address decoding in a memory device?

Answer: A demultiplexer can be used to decode the address lines in a memory device, which helps to select the desired memory location for read or write operations. The number of output lines in the demultiplexer corresponds to the number of memory locations that can be addressed.

A demultiplexer (DMUX or DEMUX) is a combinational digital circuit that takes one input and routes it to one of several possible output lines. The selection of the output line is controlled by a set of control signals, often referred to as select lines. A demultiplexer is essentially the opposite of a multiplexer (MUX), which selects one of several input lines and routes it to a single output line. The primary application of a demultiplexer is to enable data transmission from one source to multiple destinations. It is used to convert a single data stream into several data streams, and the opposite process is multiplexing, which combines several data streams into a single data stream. A common type of demultiplexer is a binary demultiplexer, which has two inputs and 2n outputs. The select lines are binary inputs that determine which output line the input signal is routed to. For example, a 2-to-4 binary demultiplexer has two input lines and four output lines. A common use of demultiplexers is in memory systems, where they are used for address decoding. For instance, a 2-to-4 demultiplexer can be used to decode the two most significant bits of a memory address, and the four output lines can be used to select one of four memory locations. In digital communication systems, demultiplexers can be used to separate a high-speed data stream into multiple lower-speed data streams, which can be processed by different devices or components. This helps to distribute the data flow and avoid data congestion. A demultiplexer can also be used for signal demodulation. For instance, in a frequency division multiplexing (FDM) system, several signals with different frequencies are combined into a single signal for transmission. At the receiving end, a demultiplexer can separate the original signals based on their frequencies. Demultiplexers can be implemented using different logic gates, such as AND gates, OR gates, and inverters. The implementation of a demultiplexer depends on the specific design requirements and the available components. In conclusion, demultiplexers are essential digital circuits that play a vital role in data transmission and communication systems. They are used to route a single input signal to multiple output lines, and the selection of the output line is controlled by a set of select lines. Demultiplexers have a wide range of applications in digital communication, memory systems, and signal processing, among others.