Preamplified two-wired active electrodes with DC-offset compensation

Instrumentation amplifiers are widely used in biosignal measurements, due to their good common mode rejection ratio (CMRR) and their high input impedance. While the fabrication of active electrodes has been reported and their beneficial effects scientifically confirmed their usage in daily practice is still limited. This work describes a new instrumentation amplifier (IA) for biopotentials based on preamplified two-wired active electrodes with a gain of 40 dB. This is possible due to the DC-offset compensation provided by an integrator in the feedback loop. The DC-offset compensation allows for the first time to simultaneously measure the amplified signal and the DC-offset between the inputs. The signal quality is improved by amplifying and buffering the signal on the electrodes.