Patent ID: 6181969
Filing Date: 2001-01-30
Classification: A61N

Abstract:
A programmable output current circuit for use within an implantable medical device having a plurality of stimulus electrodes, a selected grouping of said stimulus electrodes providing a path through which a programmable stimulus current is selectively applied, each of the plurality of electrodes having an electrode node associated therewith, the programmable output current circuit for each electrode node comprising:a set of n P-FET current sources, where n is an integer equal to 0, 1, 2, . . . n, wherein each of the n P-FET current sources is permanently attached to the electrode node, and further wherein each of the n P-FET current sources is biased to source a current to the electrode node having a programmable value of 2.sup.n I where I is a fixed current reference value; anda set of n N-FET current sources, wherein each of the n N-FET current sources is also permanently attached to the electrode node, and further wherein each of the n N-FET current sources is biased to sink a current from the electrode node having a programmable value of 2.sup.n I; andcontrol means for selectively biasing each of the n P-FET and n N-FET current sources in an enabled or disabled state;an electrode associated with each electrode node;wherein a first combination of enabled P-FET current sources, accompanied by a second combination of enabled N-FET current sources, cause a current flow to occur through a load connected between the electrodes associated with the electrode nodes of the respective sets of enabled P-FET and N-FET current sources having a magnitude equal to the sum of all the currents sourced from each of the enabled P-FET current sources, which sum is equal to the sum of all the currents sunk to each of the enabled N-FET current sources.