The common-mode rejection ratio (CMRR) of an op-amp is defined as which?
ACMRR = |Vout / Vin| under all conditions always
BCMRR = |A_d + A_cm| under all conditions always
CCMRR = |A_d / A_cm| (diff over common-mode)
DCMRR = R_in / R_out only at every frequency
Answer & Solution
Correct answer: C. CMRR = |A_d / A_cm| (diff over common-mode)
CMRR = differential-mode gain over common-mode gain, often in dB: CMRR_dB = 20·log10|A_d/A_cm|. High CMRR rejects ground noise on twisted pair / sensor lines.
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