AN ACTIVE ELECTRODE HAVING A CLOSED-LOOP UNIT-GAIN AMPLIFIER WITH CHOPPER MODULATION

摘要

An active electrode has an electrode for sensing an electric potential and generating an input signal, and a shield placed near said electrode but being electric insulated from the electrode. An integrated amplifier (10) has an input connected to the at least one electrode for receiving the input signal, and providing a buffered path outputting a buffered output signal. The shield being connected to said output of the integrated amplifier to actively drive the electrical potential of said shield, thereby providing an active shielding of said electrode. The buffered path includes a first mixer (11) in front of the integrated amplifier for frequency shifting the input signal from a basic frequency range to a higher frequency range, and a second mixer (12) on the output of the integrated amplifier for frequency shifting the amplified signal from said higher frequency range back to said basic frequency range. The active electrode may be used for recording EEG signals.