A neurostimulation comprises a plurality of electrical terminals configured for being respectively coupled to an array of electrodes, at least three configurable sources respectively coupled to at least three of the electrical terminals, and control circuitry configured for programming each of the at least three configurable sources to be either a current source or a voltage source. A method of providing neurostimulation therapy to a patient using an array of electrodes implanted adjacent neural tissue of the patient, comprises conveying electrical stimulation energy between a first one the electrodes and a second one of the electrodes, thereby creating an electrical field potential within the neural tissue, regulating a first current flowing through the first electrode, and regulating a first voltage at a third different one of the electrodes, thereby modifying a shape of the electrical field potential within the neural tissue.
