Abstract: The invention provides an electro-physiological system and various techniques for substantially canceling direct current (DC) offset while amplifying low frequency biological signals, e.g. local field potentials. In particular, the measured results of the invention show a DC offset rejection ratio of approximately greater than 100 dB. In one embodiment, the invention provides a method comprising receiving a biological signal including a frequency component and a DC (direct current) component, attenuating the frequency component of the biological signal to generate a second signal, and subtracting the second signal from the biological signal to generate a third signal.