Medical devices and methods for making and using medical devices are disclosed. An example medical device includes an ablation system. The ablation system may include an elongate shaft having a distal region. A plurality of ablation tines may be disposed at the distal region. Each of the ablation tines may include a tubular member having a flexible circuit disposed therein. The flexible circuit may include a substrate, one or more electrodes coupled to the substrate, and a temperature sensor coupled to the substrate and positioned adjacent to the one or more electrodes. The plurality of ablation tines may include a first ablation tine and a second ablation tine. A pair of bipolar electrodes may defined by a first electrode disposed at the first ablation tine and a second electrode disposed at the second ablation tine.