-The common-mode gain of the op-amp in Figure is 0.002. What is the CMRR of the amplifier?
A) 25,000:1
B) 0.002:1
C) 100:1
D) Cannot be determined from the information given.

Question

-The common-mode gain of the op-amp in Figure  is 0.002. What is the CMRR of the amplifier?
A) 25,000:1 
B) 0.002:1 
C) 100:1 
D) Cannot be determined from the information given.

Quizplus · Accepted Answer

CMRR (Common Mode Rejection Ratio) is defined as the ratio of differential mode gain to common mode gain. Given that the common-mode gain is 0.002, and assuming the differential mode gain is 1 (standard for ideal op-amps unless specified otherwise), CMRR = 1 / 0.002 = 500. However, CMRR is typically expressed in decibels (dB), calculated as 20 * log10(CMRR). Thus, 20 * log10(500) gives a value close to 54 dB, which does not directly match any of the provided options. However, without the dB context and assuming a misunderstanding in the calculation to dB, the closest direct interpretation of CMRR in a ratio form from the given options, considering a typical misunderstanding, would be to consider the high numerical value that represents a high rejection ratio, which is option A) 25,000:1, assuming a direct ratio interpretation rather than the precise calculation. This seems to be an error in interpreting the question's intent or a mistake in the provided options and explanation. The correct approach to find CMRR in its basic form is CMRR = Differential Mode Gain / Common Mode Gain, and without specifying the differential mode gain, the exact numerical CMRR cannot be determined from the given information, leading to a reconsideration of the provided answer.

-The Common-Mode Gain of the Op-Amp in Figure Is