Near-field energy transmitters for charging a rechargeable power source of an implantable medical device (IMD). In some cases, the transmitter may include an output driver that may drive a transmit coil such that near-field energy is transmitted to the IMD at a determined frequency. In some cases, the IMD may include a receiving coil that may capture the near-field energy and then convert the near-field energy into electrical energy that may be used to recharge the rechargeable power source. Since the rechargeable power source does not have to maintain sufficient energy stores in a single charge for the entire expected life of the IMD, the power source itself and thus the IMD may be made smaller while still meeting device longevity requirements.