Abstract: There is described are electroencephalography (EEG) device. The EEG device comprises one or more inputs for connecting via electrodes to a subject, and one or more DC/AC EEG amplifiers for amplifying electric potential signals from a subject. Each DC/AC EEG amplifier comprises a preamplifier connected to the one or more inputs and configured to amplify a signal received at the one or more inputs, the preamplifier having a differential gain set so as to have a common mode rejection ratio (CMRR) of at least 100 dB. Each DC/AC EEG amplifier further comprises an amplifier circuit connected to the preamplifier and configured to further amplify the signal, and, based thereon, output an output signal comprising a DC component having a frequency of less than 0.02 Hz.