Current generation architecture for an implantable stimulator device having coarse and fine current control

An implantable stimulator device (100) comprising: a plurality of electrodes (E1, EN) implantable adjacent to tissue to be stimulated, a first generation circuitry stream comprising a plurality of first stages (403, 410) in which the first stages are distributed among the electrodes such that any first stage can generate a current at any particular electrode; and characterized by a second circuitry (403) stream comprising a plurality of second stages (409), wherein each of the second stages is directly coupled to a particular one of the electrodes to generate a current at each electrode.