Signal sensing in an implanted apparatus with an internal reference

An apparatus for sensing biological signals from an animal, the apparatus comprising:

• an electrode pair adapted for implantation in the animal at intravascular locations to sense biological signals;
• a pair of insulated conductors connected to the at least one electrode pair;
• a passive network of filters connected to the pair of insulated conductors and configured to filter the biological signals and thereby produce filtered biological signals;
• an instrumentation amplifier connected to the passive network of filters and having an internal voltage reference, the instrumentation amplifier being configured to amplify the filtered biological signals to produce an amplified signal, wherein the internal voltage reference also is connected to a node in the passive network of filters;
• and
• an energy source powering the apparatus and being isolated from all ground connections to the animal and external to the animal;
• and
• a signal analysis module configured to analyze the amplified signal.

An apparatus for sensing biological signals from an animal, the apparatus comprising:

• at least one electrode pair disposed at a first set of locations to sense biological signals;
• a pair of insulated conductors connected to the at least one electrode pair, the pair of insulated conductors being closely spaced to minimize sensitivity to electromagnetic interference;
• an internal reference module configured to provide an internal reference voltage;
• a filter network connected to the pair of insulated conductors and configured to provide a filtered biological signal, the filter network comprising at least one high pass filter and at least one low pass filter, the high pass filter configured to provide AC coupling and the low pass filter configured to provide noise rejection, wherein the internal reference voltage is applied to a node of one of the at least one low pass filter;
• an instrumentation amplifier connected to the filter network, the instrumentation amplifier configured to receive the internal reference voltage, and to amplify the filtered biological signal to provide an amplified biological signal;
• an energy source powering the apparatus, the energy source configured to be free of a wired connection to an energy supply external to the animal;
• and
• a signal analysis module configured to analyze the amplified differential signal to extract at least one physiological parameter of the animal;
• wherein the apparatus is substantially free of all wired ground connections to a ground external to the apparatus.