What characteristic of a differential amplifier allows recording of low amplitude EEG signals amidst noise?

The common mode rejection characteristic of a differential amplifier is crucial for effectively recording low amplitude EEG signals in the presence of noise. Differential amplifiers are designed to amplify the difference between two input signals while simultaneously rejecting any signals that are common to both inputs. This means that any noise that affects both inputs equally—such as electrical interference from nearby equipment or muscle artifacts—will be minimized in the output.

By emphasizing the differential signal, which represents the actual brain activity being recorded, the amplifier significantly enhances the ability to extract meaningful EEG data while discarding unwanted noise. This is vital in EEG recordings, where the brain signals are often small and easily obscured by external disturbances. Thus, the common mode rejection ratio (CMRR) is an essential parameter that determines the quality of EEG recordings, making it a key characteristic for effectively capturing low amplitude signals against a backdrop of noise.