The method involves attaching an electrode (16) to an electrical source i.e. direct current (DC) or alternating current (AC) voltage source, to be connected with a counter-electrode (17). Electrical tissue resistance is determined between the electrodes. An output voltage i.e. high-frequency AC voltage, is output from the source and controlled through the determined tissue resistance. A functional relationship having parameters e.g. open-circuit voltage, is determined for controlling the output voltage depending on a function of the determined tissue resistance. Independent claims are also included for the following: (1) a method for tissue fusion or coagulation using an electrode (2) a device for tissue fusion or coagulation by high-frequency AC current.
