Integrated Circuit (IC) Noise MCQ [Free PDF] - Objective Question Answer for Integrated Circuit (IC) Noise Quiz

1. The major source of the interference with the desired signal in an electronic system is called

A. Error signal
B. Interference signal
C. Noise signal
D. Faulty signal

Answer: C

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

Answer: B

In any electronics system, noise can come from many external sources as a result of the 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

Answer: B

Except for lightning, the remaining are self-induced or internal noises. Lightning is a natural phenomenon of external noise sources.

4. The type of noise phenomena that increases with an increase in temperature is

A. 1/f noise
B. Schottky noise
C. Thermal noise
D. None of the mentioned

Answer: D

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 the circuit
D. All of the mentioned

Answer: A

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 the circuit

All the factors determine the amount of noise induced in a given circuit.

6. Which type of noise is produced when the op-amp has wider bandwidth?

A. 1/f noise
B. Schottky noise
C. Thermal noise
D. Radiant noise

Answer: B

When the op-amp has a 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

Answer: C

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
B. Input lead length short
C. Both input and output lead length short
D. Output lead length short

Answer: C

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

Answer: B

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 the best immunity to induced noise?

A. Non-inverting amplifier
B. Inverting amplifier
C. Differential amplifier
D. Voltage follower

Answer: C

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

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

A. V_O= -[(R_F/R₁)×V_d]+V_no
B. V_O= -(R_F/R₁)×(V_d/V_no)
C. V_O= -[(R_F/R₁)×V_d]-V_no
D. V_O= -[(R_F/R₁)×V_d]×V_no

Answer: A

As the input of the differential amplifier is provided with induced noise voltage, the output voltage will be equal to

V_o=-[(R_F/R₁)×V_d]+V_no

Where V_no–> Output noise.

12. When does the op-amp said to operate in a common-mode configuration?

A. When the input voltage is equal
B. When the input voltage is equal to the output voltage
C. When the same voltage is applied to both input terminals of an op-amp
D. When different voltage is applied to both input and terminal of an op-amp

Answer: C

When the same input voltage is applied to both input terminals of an op-amp, the op-amp is said to be operating in a common mode configuration.

13. Common mode voltage gain of an op-amp is generally

A. >1
B. =1
C. <1
D. None of the mentioned

Answer: C

The amplitude of common-mode output voltage is very small and often insignificant compared to the common-mode input voltage. Therefore, the common-mode voltage gain is generally much smaller than 1.

14. Define the common-mode rejection ratio (CMRR) of op-amp?

A. CMRR=A_D/A_CM
B. CMRR=A_CM/ A_D
C. CMRR=V_OCM/A_CM
D. CMRR=A_D*A_CM

Answer: A

CMRR is defined as the ratio of the differential gain to the common-mode gain, that is CMRR=A_D/A_CM.

15. Find the correct equation for common-mode rejection ratio

A. CMRR = 20log(A_D/ A_CM)
B. CMRR = 20log(V_io/ V_CM)
C. CMRR = (A_D* V_CM)/ V_OCM
D. All of the mentioned

Answer: D

Generally, the CMRR value is very large and usually specified in decibels (dB. Also, the CMRR value can establish a relationship with common-mode output voltage.

16. When an op-amp exhibits poor common-mode rejection?

A. Small common-mode output voltage
B. Large common-mode output voltage
C. Negligible common-mode output voltage
D. None of the mentioned

Answer: B
A large common-mode output voltage for a given common-mode input voltage indicates a large degree of imbalance between the two input terminals or poor CMRR.

17. Higher value of the common-mode rejection ratio can be reached

A. By reducing the common-mode voltage
B. By decreasing the differential gain
C. By reducing the common-mode input voltage
D. All of the mentioned

Answer: D

CMRR =(A_D* V_CM)/ V_OCM, this equation indicates that the higher the value of CMRR, the smaller will be the amplitude of the output common-mode voltage.

18. Variation in the operating frequency of op-amp causes

A. Variation in gain amplifier
B. Variation in gain phase angle
C. Variation in gain amplitude and its phase angle
D. None of the mentioned

Answer: C

The gain of the op-amp is a function of frequency. It will have a specific magnitude as well as a phase angle.

19. A graph of the magnitude of the gain versus frequency is called

A. Break frequency
B. Frequency response plot
C. Frequency stability plot
D. Transient response plot

Answer: B

A frequency response plot is obtained by plotting the gain of the op-amp responding to different frequencies.

20. In the frequency response plot, the frequency is expressed in

A. Anti-logarithmic scale
B. Logarithmic scale
C. Linear scale
D. Exponential scale

Answer: B

To accommodate large frequency ranges the frequency is assigned to a logarithmic scale.

21. Why the gain magnitude in the frequency response plot is expressed in decibels (dB.

A. To obtain gain > 10⁵
B. To obtain gain < 10⁵
C. To obtain gain = 0
D. To obtain gain = ∞

Answer: A

In the frequency response plot, gain magnitude is assigned a linear scale and is expressed in decibels to accommodate very high gain ( ≅ of the order 10⁵ or higher).

22. Which technique is used to determine the stability of op-amp?

A. Frequency response plot
B. Transient response plot
C. Bode plot
D. All of the mentioned

Answer: C

Although frequency response and bode plots indicate the effect of frequency variation on gain, the Bode plot is generally used for stability determination and network design.

23. How many types of plots can be obtained in the AC analysis of the network using the Bode plot?

A. Five
B. Four
C. Three

Answer: D

Two types of plots can be obtained using the Bode plot. They are magnitude versus frequency and phase angle versus frequency plots.

24. What happens when the operating frequency of op-amp increases?

A. Gain of the amplifier decrease
B. Phase shift between output and input signal decrease
C. Gain and phase shift of amplifier decreases
D. None of the mentioned

Answer: A

When the operating frequency has increased the gain of the amplifier decrease. As it is linearly related to frequency, the phase shift is logarithmically related to frequency.

25. Which of the following causes change in gain and phase shift?

A. Internally integrated Resistor
B. Internally integrated inductors
C. Internally integrated Capacitor
D. All of the mentioned

Answer: C

The change in function of frequency is attributed to the internally integrated capacitor as well as a stray capacitor. These capacitors are due to the physical characteristic of the semiconductor device.

26. Which plot is not provided by the manufacturers?

A. Magnitude plot
B. Phase angle plot
C. Frequency response plot
D. None of the mentioned

Answer: B

Phase angle plots are not generally provided because phase shifts of later generation op-amp are less than 90^o even at cross-over frequency.

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