Current generation architecture for an implantable medical device

A stimulator device system, comprising:

• an electrode node configured to be coupled to an electrode to provide stimulation pulses to a patient's tissue;
• a digital-to-analog converter (DAC) configured to amplify a reference current to a first current at a first node;
• one or more first transistors configured to receive the first current from the first node,
• a plurality of first branches each comprising one or more second transistors and configured when selected to produce a first branch current, wherein each first branch current comprises a scaled version of the first current, wherein each of the first branches terminates at a second node coupled to the electrode node,
• first amplifier circuitry configured to hold the first node and the second node to a reference voltage;
• and
• wherein a first output current is provided at the electrode node comprising a sum of the first branch currents of the selected first branches.