A current generation architecture for an implantable stimulator device such as an Implantable Pulse Generator (IPG) is disclosed. Current source and sink circuitry are both divided into coarse and fine portions, which respectively can provide coarse and fine current resolutions to a specified electrode on the IPG. The coarse portion is distributed across all of the electrodes and so can source or sink current to any of the electrodes. The coarse portion is divided into a plurality of stages, each of which is capable via an associated switch bank of sourcing or sinking a coarse amount of current to or from any one of the electrodes on the device. The fine portion of the current generation circuit preferably includes source and sink circuitry dedicated to each of the electrode on the device, which can comprise digital-to-analog current converters (DACs).