Which statement best describes common mode rejection?

Which statement best describes common mode rejection?

• A. It reduces noise that is present on both input leads
• B. It increases signal amplitude
• C. It delays sampling
• D. It changes filter characteristics

Answer: (A)

Common mode rejection describes how a differential measurement system minimizes noise that appears equally on both input leads. When interference affects both lines in the same way, the differential amplifier subtracts one input from the other, canceling out the common noise and preserving the true signal difference. That’s why the statement that best captures this concept is that it reduces noise present on both input leads. The other ideas describe different aspects—signal gain, timing delay, or filter characteristics—not the suppression of identical noise on both inputs.

Common mode rejection describes how a differential measurement system minimizes noise that appears equally on both input leads. When interference affects both lines in the same way, the differential amplifier subtracts one input from the other, canceling out the common noise and preserving the true signal difference. That’s why the statement that best captures this concept is that it reduces noise present on both input leads. The other ideas describe different aspects—signal gain, timing delay, or filter characteristics—not the suppression of identical noise on both inputs.