1. A neurostimulation system, comprising: at least one lead to provide an array of electrodes; a plurality of electrical terminals configured to be electrically connected to the array of electrodes via the at least one lead; at least three configurable sources respectively coupled to at least three of the electrical terminals, each of the configurable sources including a current source and a voltage source and each of the configurable sources being capable of being programmed to operate as the current source and being capable of being programmed to operate as the voltage source; and control circuitry configured for programming each of the at least three configurable sources to be either the current source or the voltage source, wherein the control circuitry is configured to: program at least one of the configurable sources to operate as the current source and to connect the current source to at least one electrode in the array of electrodes to generate a current distribution in neural tissue; and program at least one other of the configurable sources to operate as the voltage source and to connect the voltage source to at least one other electrode in the array of electrodes to shape the current distribution.