The ability of an amplifier to cancel external interference that is common to both input signals is called?

The ability of an amplifier to cancel external interference that is common to both input signals is called?

• A. High frequency filter
• B. Sampling rate
• C. System referencing
• D. Common mode rejection

Answer: (D)

Common mode rejection is the ability of an amplifier to reject interference that is present on both input lines. A differential amplifier amplifies only the difference between its two inputs, so noise or interference that appears identically on both inputs—the same stray signal picked up by lead wires or surrounding equipment—tends to cancel out. The stronger this rejection, the cleaner the output signal, which is essential in sleep studies where small physiological signals (like EEG) can be easily masked by common-mode noise such as mains hum. This capability is quantified as the common-mode rejection ratio (CMRR), typically expressed in decibels; a higher CMRR means better suppression of that unwanted, common signal. Other options describe different concepts (filters target frequency ranges, sampling rate determines data points per second, referencing pertains to grounding), and do not capture the specific idea of removing identical interference on both inputs.

Common mode rejection is the ability of an amplifier to reject interference that is present on both input lines. A differential amplifier amplifies only the difference between its two inputs, so noise or interference that appears identically on both inputs—the same stray signal picked up by lead wires or surrounding equipment—tends to cancel out. The stronger this rejection, the cleaner the output signal, which is essential in sleep studies where small physiological signals (like EEG) can be easily masked by common-mode noise such as mains hum. This capability is quantified as the common-mode rejection ratio (CMRR), typically expressed in decibels; a higher CMRR means better suppression of that unwanted, common signal. Other options describe different concepts (filters target frequency ranges, sampling rate determines data points per second, referencing pertains to grounding), and do not capture the specific idea of removing identical interference on both inputs.