Implantable pulse generators and spinal cord stimulation (SCS) systems are provided. The implantable pulse generator comprises telemetry circuitry configured for wirelessly receiving programming signals from an external programmer, and a plurality of bi-directional current sources configured for being respectively coupled to a plurality of electrodes. The implantable pulse generator further comprises control circuitry configured for directing the bi-directional current sources to output current pulses of a selected amplitude and polarity to the electrodes in accordance with the programming signals. The SCS system may comprise a plurality of electrodes, an external programmer configured for transmitting programming signals, and the afore-described implantable pulse generator as described above. In one embodiment, the SCS system further comprises one or more stimulation leads carrying the electrodes, in which case, the implantable pulse generator may further include a connector removably mated to the stimulation lead(s).