A follower amplifier with power supply biased by a controlled voltage source such that the power supply potentials are, for the frequencies of interest, as close as possible to the potential of the follower output. There is proposed a front-end electronic circuit for biopotential and impedance measurements with outstanding performances (very high input impedance and gain very close to unity). Preferably, the explicit guard electrode and the explicit electronic unit at the belt are no longer necessary; all electronics is embedded in units placed directly at the measurement sites. Moreover, the proposed front-end electronic circuit allows a drastic simplification of the cabling and connectors since all units are connected to only one wire (the theoretical minimum) for potential reference and current return. Preferably, this wire does not even require an electrical isolation and can be easily embedded in the textile of a shirt, in a garment, mesh, belt, etc.