What is the CMRR in decibels (dB) for a typical 741C op-amp? Given the typical open-loop differential gain for the 741C is 200,000 and the typical commonmode gain is 6.3.
The CMRR in decibels (dB) for a typical 741C op-amp can be calculated using the formula:
CMRR(dB) = 20 log10 (open-loop differential gain / common-mode gain)
Substituting the values given:
CMRR(dB) = 20 log10 (200,000 / 6.3)
CMRR(dB) = 20 log10 (31,746.03)
CMRR(dB) = 90.31 dB (rounded to two decimal places)
The common-mode rejection ratio (CMRR) measures the ability of an op-amp to reject signals that are common to both its inputs.
CMRR is defined as:
CMRR(dB) = 20 * log10(open-loop differential gain / common-mode gain)
Given that the typical open-loop differential gain for the 741C op-amp is 200,000 and the typical common-mode gain is 6.3, we can substitute these values into the formula:
CMRR(dB) = 20 * log10(200,000 / 6.3)
Calculating this expression, we get:
CMRR(dB) = 20 * log10(31,746)
Using a calculator, we find:
CMRR(dB) ≈ 94.999 dB
Therefore, the CMRR for a typical 741C op-amp is approximately 94.999 dB.