An electrosurgical medical device 1 is described having a handle 5, a shaft 3 coupled to the handle 5 and an end effector 7 coupled to the shaft 3. The end effector 7 has at least one electrode for providing electrical signals to a tissue or vessel to be treated. An RF drive circuit is provided for generating an RF drive signal that is applied to the end effector electrode. The RF drive circuit includes a resonant circuit and a frequency controller is used to vary the frequency of a signal passed through the resonant circuit in order to control the power supplied to the end effector electrode.
