# Linear Integrated Circuit Questions and Answers – Noise

This set of Linear Integrated Circuit Multiple Choice Questions & Answers (MCQs) focuses on “Noise”.

1. The major source of interference with the desired signal in electronic system is called
a) Error signal
b) Interference signal
c) Noise signal
d) Faulty signal

Explanation: Any unwanted signal associated with the desired signal is noise.

2. Identify the external noise sources
a) Switching of rotating machinery
b) Control circuits
c) Ignition system
d) All of the mentioned

Explanation: In any electronics system, noise can come from many external sources as a result of circuitry itself.

3. Which among the following is not a source of internal noise?
a) AC random voltages generated within conductors
b) Lightning
c) Switching of circuits
d) None of the mentioned

Explanation: Except lightning the remaining are self induced or internal noises. Lightning is a natural phenomenon of external noise source.

4. The type of noise phenomena that increases with increase in temperature is
a) None of the mentioned
b) 1/f noise
c) Schottky noise
d) Thermal noise

Explanation: The thermal noise increases with an increase in temperature.

5. The factors that determine the amount of noise induced is
a) Type of coupling between two circuits
b) Rate of change of current per unit time
c) Speed of operation of circuit
d) All of the mentioned

Explanation: All the factors determine the amount of noise induced in a given circuit.
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6. Which type of noise is produced when the op-amp has wider bandwidth?
a) 1/f noise
b) Schottky noise
c) Thermal noise

Explanation: When the op-amp has wide bandwidth, schottky noise is produced. The amount of schottky noise is greater with wider bandwidth and large resistance.

7. Mention a scheme to reduce the effect of electrical noise on ICs?
a) Isolating ICs on different boards
b) Add a filter near ICs
c) Physical shielding of ICs
d) Use of compensating networks near ICs

Explanation: Physical shielding of the ICs and associated wiring helps to prevent external electromagnetic radiation from inducing noise into the internal circuitry.

8. Internal noise generation can be reduced by keeping
a) None of the mentioned
c) Both input and output lead length short

Explanation: The common way of reducing the internal noise generation is by keeping input and output lead length as short as practically possible.

9. How to choose an IC for a high electrical noise environment?
a) Low degree of noise immunity
b) High degree of noise immunity
c) Low degree of noise reduction
d) High degree of noise reduction

Explanation: In a high electrical noise environment an IC with a high degree of noise immunity will minimize the amount of special care needed for proper circuit operation.

10. Which among the following has best immunity to induced noise?
a) Non-inverting amplifier
b) Inverting amplifier
c) Differential amplifier
d) Voltage follower

Explanation: The differential amplifier offers best immunity to induced noise because, the ratio of the output noise voltage to the input noise voltage in practice will be much smaller that unity.

11. Find the output voltage for differential amplifier, Where Vin->Induced input noise.

a) VO= -[(RF/R1)×Vd]+Vno
b) VO= -(RF/R1)×(Vd/Vno)
c) VO= -[(RF/R1)×Vd]-Vno
d) VO= -[(RF/R1)×Vd]×Vno

Explanation: As the input of the differential amplifier is provided with induced noise voltage, the output voltage will be equal to Vo=-[(RF/R1)×Vd]+Vno
Where Vno–> Output noise.

Sanfoundry Global Education & Learning Series – Linear Integrated Circuits.

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