Comparators MCQ Quiz - Objective Question with Answer for Comparators - Download Free PDF

Explanation:

Error Detector (Comparator)

Definition: An error detector, commonly referred to as a comparator, is an electronic device or circuit that compares two input signals and determines the difference between them. It is widely used in control systems, instrumentation, and signal processing to ensure the desired performance and identify deviations or errors. The comparator plays a crucial role in maintaining the stability and accuracy of systems by continuously monitoring and correcting errors.

Working Principle:

The comparator operates by comparing an input signal (usually the actual state or condition of a system) with a reference signal (desired state or condition). The difference between these signals is called the error signal. This error signal is then processed to make adjustments to the system, bringing it closer to the desired state.

• Input signals: The comparator receives two inputs – the reference signal and the actual signal.
• Comparison: The comparator compares these inputs and calculates the error signal.
• Output: The error signal is generated, which can be used to trigger corrective actions or adjustments in the system.

Applications:

• Control Systems: Comparators are extensively used in control systems, such as PID controllers, where the error signal is utilized to adjust system parameters and achieve stability and precision.
• Instrumentation: Error detectors are employed in measurement and instrumentation systems to ensure accurate readings by identifying discrepancies between actual and expected values.
• Signal Processing: Comparators are used in circuits for signal processing, such as in analog-to-digital converters, oscillators, and pulse width modulation (PWM) circuits.

Advantages:

• Provides high precision in detecting errors.
• Enables corrective measures to maintain system stability and accuracy.
• Simple and cost-effective design for many applications.

Disadvantages:

• May require additional components for complex systems to process the error signal effectively.
• Limited functionality in systems with highly nonlinear behavior.

Correct Option Analysis:

The correct option is:

Option 3: Comparator

In the context of error detection, a comparator functions as an error detector by comparing two signals – the actual state of the system and the desired state – and generating an error signal. This error signal helps in identifying deviations and initiating corrective actions. Comparators are fundamental components in control systems, ensuring the system operates as intended.

Additional Information

To further understand the analysis, let’s evaluate the other options:

Option 1: Multiplexer

A multiplexer is a device used to select one input signal from multiple input signals and forward it to a single output line. It does not perform error detection or comparison between signals. Instead, its primary function is to manage multiple data streams and direct them appropriately, which is unrelated to the functionality of error detectors.

Option 2: Decoder

A decoder is a device that translates encoded data into its original format. For example, in digital systems, it converts binary codes into human-readable formats or specific outputs. While decoders play a crucial role in communication and data processing systems, they do not perform error detection or signal comparison, which is the primary function of an error detector.

Option 4: Integrator

An integrator is a circuit that performs mathematical integration on an input signal, producing an output that represents the cumulative sum of the input signal over time. Integrators are commonly used in signal processing and control systems for tasks like smoothing signals or calculating areas under curves. However, they do not serve as error detectors or comparators.

Conclusion:

An error detector, or comparator, is an essential component in electronic systems, particularly in control and instrumentation applications. Its ability to compare signals and generate an error signal enables accurate monitoring and corrective actions to maintain system stability and performance. While other devices like multiplexers, decoders, and integrators serve important roles in electronic systems, they do not perform the function of error detection. Therefore, the correct option for this question is Option 3: Comparator.

Comparator

A magnitude digital Comparator is a combinational circuit that compares two digital or binary numbers in order to find out whether one binary number is equal, less than, or greater than the other binary number.

For N ≤ 2^k bit comparator circuit, k output lines are required.

Calculation

Given, N = 5

5 ≤ 2^k

k = 3

• 74LS85 is a 4-bit magnitude comparator of two binary format inputs.
• 74LS85 can compare two 4-bit binary data and output can be given in a 3-bit parallel form.
• The IC has low power consumption and gives output in the TTL form which makes it compatible with other TTL devices and microcontrollers.

The block diagram is as shown:

2-bit comparator

A comparator used to compare two binary numbers each of two bits is called a 2-bit magnitude comparator.

It consists of four inputs and three outputs to generate less than, equal to, and greater than between two binary numbers.

The truth table for the 2-bit comparator is given below:

The output of the A=B is:

 \(Y=\overline{A_1}\space \overline{A_0}\space \overline{B_1}\space \overline{B_0}+\overline{A_1}\space {A_0}\space \overline{B_1}\space {B_0}+{A_1}\space {A_0}\space {B_1}\space {B_0}+{A_1}\space \overline{A_0}\space {B_1}\space \overline{B_0}\)

\(Y=\overline{A_1}\space \overline{B_1}({\overline{A_0}\space \overline{B_0}}+A_0B_0)+{A_1}\space {B_1}({\overline{A_0}\space \overline{B_0}}+A_0B_0)\)

Y = (A₁⊙ B₁) (A_o ⊙ B_o)

​For applications where measurement of a physical quantity is involved, an instrumentation amplifier type op-amp circuit is recommended.

Instrumentation Amplifier:

An instrumentation amplifier is usually employed to amplify low-level signals, rejecting noise and interference signals. Therefore, the characteristics of a good Instrumentation amplifier should include:

Finite, Accurate and Stable Gain: Since the instrumentation amplifiers are required to amplify very low-level signals from the transducer device, high and finite gain is the basic requirement. The gain also needs to be accurate and the closed-loop gain must be stable.

High Input Impedance: To avoid the loading of input sources, the input impedance of the instrumentation amplifier must be very high (ideally infinite).

Low Output Impedance: The output impedance of a good instrumentation amplifier must be very low (ideally zero), to avoid loading effect on the immediate next stage.

High CMRR: The output from the transducer usually contains common-mode signals, when transmitted over long wires. A good instrumentation amplifier must amplify only the differential input, completely rejecting common-mode inputs. Thus, the CMRR of the instrumentation amplifier must be ideally infinite.

High Slew Rate: The slew rate of the instrumentation amplifier must be as high as possible to provide maximum undistorted output voltage swing.

Low Power Consumption: A good Instrumentation amplifier have low input offset currents and therefore has very low power consumption which is always a desirable property.

2-bit comparator

A comparator used to compare two binary numbers each of two bits is called a 2-bit magnitude comparator.

It consists of four inputs and three outputs to generate less than, equal to, and greater than between two binary numbers.

The truth table for the 2-bit comparator is given below:

The output of the A=B is:

 \(Y=\overline{A_1}\space \overline{A_0}\space \overline{B_1}\space \overline{B_0}+\overline{A_1}\space {A_0}\space \overline{B_1}\space {B_0}+{A_1}\space {A_0}\space {B_1}\space {B_0}+{A_1}\space \overline{A_0}\space {B_1}\space \overline{B_0}\)

\(Y=\overline{A_1}\space \overline{B_1}({\overline{A_0}\space \overline{B_0}}+A_0B_0)+{A_1}\space {B_1}({\overline{A_0}\space \overline{B_0}}+A_0B_0)\)

Y = (A₁⊙ B₁) (A_o ⊙ B_o)

• 74LS85 is a 4-bit magnitude comparator of two binary format inputs.
• 74LS85 can compare two 4-bit binary data and output can be given in a 3-bit parallel form.
• The IC has low power consumption and gives output in the TTL form which makes it compatible with other TTL devices and microcontrollers.

The block diagram is as shown:

Comparator

A magnitude digital Comparator is a combinational circuit that compares two digital or binary numbers in order to find out whether one binary number is equal, less than, or greater than the other binary number.

For N ≤ 2^k bit comparator circuit, k output lines are required.

Calculation

Given, N = 5

5 ≤ 2^k

k = 3

The only possible combinations are

A = 01 and B = 0 0

A = 10 and B = 00, 01

A = 11 and B = 00, 01, 10

So there are only 6 combinations

Tips and Tricks:

\(\frac{2^{2n} - 2^n}{2}\)

where n = 2 bit

Concept:

The conversion time of different types of n-bit ADC is shown :

• From the above table, it is clear that the dual-slope is the slowest ADC and Flash Type is the fastest ADC.
• The conversion type of Flash type is independent of the number of bits 

Application:

n = 8

• Maximum conversion time in clock cycles of 8-bit Successive approximation type ADC  = n=  8
• Maximum conversion time in clock cycles of 8 bit Dual slope type ADC = 2n+1 = 2⁹ = 512
• Maximum conversion time in clock cycles of 8 bit Successive approximation type ADC = 1

x = x₁ x₀ y = y₁ y₀

The Boolean function S that satisfies condition,

If x > y, then s = 1.

We can represent the above condition through a truth table.

By using k-maps

Minimized form:

s = x₁y̅₁ + x₁x₀y̅₀ + x₀y̅₁y̅₀

2-bit comparator

A comparator used to compare two binary numbers each of two bits is called a 2-bit magnitude comparator.

It consists of four inputs and three outputs to generate less than, equal to, and greater than between two binary numbers.

The truth table for the 2-bit comparator is given below:

The output of the A=B is:

 \(Y=\overline{A_1}\space \overline{A_0}\space \overline{B_1}\space \overline{B_0}+\overline{A_1}\space {A_0}\space \overline{B_1}\space {B_0}+{A_1}\space {A_0}\space {B_1}\space {B_0}+{A_1}\space \overline{A_0}\space {B_1}\space \overline{B_0}\)

\(Y=\overline{A_1}\space \overline{B_1}({\overline{A_0}\space \overline{B_0}}+A_0B_0)+{A_1}\space {B_1}({\overline{A_0}\space \overline{B_0}}+A_0B_0)\)

Y = (A₁⊙ B₁) (A_o ⊙ B_o)

• 74LS85 is a 4-bit magnitude comparator of two binary format inputs.
• 74LS85 can compare two 4-bit binary data and output can be given in a 3-bit parallel form.
• The IC has low power consumption and gives output in the TTL form which makes it compatible with other TTL devices and microcontrollers.

The block diagram is as shown:

Comparator

A magnitude digital Comparator is a combinational circuit that compares two digital or binary numbers in order to find out whether one binary number is equal, less than, or greater than the other binary number.

For N ≤ 2^k bit comparator circuit, k output lines are required.

Calculation

Given, N = 5

5 ≤ 2^k

k = 3

The only possible combinations are

A = 01 and B = 0 0

A = 10 and B = 00, 01

A = 11 and B = 00, 01, 10

So there are only 6 combinations

Tips and Tricks:

\(\frac{2^{2n} - 2^n}{2}\)

where n = 2 bit