Active electrode having a closed-loop unit-gain amplifier with chopper modulation

A sensor system for sensing an electric potential difference, comprising:

• at least one set of electrodes including a reference electrode providing an electric potential reference;
• a sensing electrode providing a measurement point for measuring an electrical potential relative to said reference electrode;
• and
• a differential amplifier receiving input from said sensing electrode and said reference electrode and generating an output signal representing the electrical potential difference between said sensing electrode and said reference electrode;
• wherein at least one electrode of said least one set of electrodes being an active electrode component having an electrode for sensing a bio potential and adapted for providing a bio potential signal, and furthermore comprising:
• a shield placed adjacent to and electrically insulated from said sensing electrode;
• an integrated amplifier component adapted for providing a buffered signal path and comprising:
• a first mixer for frequency shifting the bio potential signal from a basic frequency range to a higher frequency range,
• an integrated amplifier receiving the frequency shifted signal from the first mixer, and having a unit-gain maintained at least in part by a feedback signal on a feedback branch from a first point downstream of said
• integrated amplifier to a second point upstream of said integrated amplifier, and a second mixer for frequency shifting an output signal from the integrated amplifier from the higher frequency range to the basic frequency range,
• the integrated amplifier component being configured as a chopper modulation amplifier outputting a buffered output signal;
• wherein an output of the integrated amplifier component is connected to the shield,
• the integrated amplifier component being adapted for actively driving the electrical potential of the shield and thereby providing an active shielding of the sensing electrode,
• whereby the shield adjacent to the sensing electrode receives the buffered output signal, and wherein said first point is downstream of said second mixer and said second point is upstream of said first mixer.

An active electrode component having an electrode for sensing a bio potential and adapted for providing a bio potential signal, and furthermore comprising:

• a shield placed adjacent to and electrically insulated from said electrode;
• an integrated amplifier component adapted for providing a buffered signal and comprising:
• a first mixer formed on an integrated circuit chip for frequency shifting the bio potential signal from a basic frequency range to a higher frequency range,
• an integrated amplifier formed on said integrated circuit chip and receiving the frequency shifted signal from the first mixer, and having a unit-gain, and
• a second mixer formed on said integrated circuit chip for frequency shifting an output signal from the integrated amplifier from the higher frequency range to the basic frequency range,
• the integrated amplifier component being configured as a chopper modulation amplifier outputting a buffered output signal;
• wherein an output of the integrated amplifier component is connected to the shield,
• the integrated amplifier component being adapted for actively driving an electrical potential of the shield and thereby providing an active shielding of the electrode,
• whereby the shield adjacent to the electrode receives the buffered output signal,
• wherein said first mixer receives two input signals and provides first and second chopped output signals, and said integrated amplifier is a differential amplifier having first and second inputs each coupled to receive a respective one of said chopped output signals, and
• wherein said second input of said first mixer is connected to receive a feedback signal derived from the output of said integrated amplifier.

A sensor system for sensing an electric potential difference, comprising:

• at least one set of electrodes including a reference electrode providing an electric potential reference;
• a sensing electrode providing a measurement point for measuring an electrical potential relative to said reference electrode;
• and
• a differential amplifier receiving input from said sensing electrode and said reference electrode and generating an output signal representing the electrical potential difference between said sensing electrode and said reference electrode;
• wherein at least one electrode of said least one set of electrodes being an active electrode component having an electrode for sensing a bio potential and adapted for providing a bio potential signal, and furthermore comprising:
• a shield placed adjacent to and electrically insulated from said electrode;
• an integrated amplifier component adapted for providing a buffered signal and comprising:
• a first mixer for frequency shifting the bio potential signal from a basic frequency range to a higher frequency range,
• an integrated amplifier receiving the frequency shifted signal from the first mixer, and having a unit-gain, and
• a second mixer for frequency shifting an output signal from the integrated amplifier from the higher frequency range to the basic frequency range,
• the integrated amplifier component being configured as a chopper modulation amplifier outputting a buffered output signal;
• wherein an output of the integrated amplifier component is connected to the shield,
• the integrated amplifier component being adapted for actively driving the electrical potential of the shield and thereby providing an active shielding of the sensing electrode,
• whereby the shield adjacent to the sensing electrode receives the buffered output signal,
• wherein said first mixer receives two input signals and provides first and second chopped output signals, and said integrated amplifier is a differential amplifier having first and second inputs each coupled to receive a respective one of said chopped output signals, and
• wherein said second input of said first mixer is connected to receive a feedback signal derived from the output of said integrated amplifier.