Common Mode Rejection Ratio MCQ [Free PDF] - Objective Question Answer for Common Mode Rejection Ratio Quiz

1. 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.

2. 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.

3. 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.

4. 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.

5. 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.

6. 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.

7. 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.

8. 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.

9. 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.

10. 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).

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