A surgical instrument for supplying energy to tissue can comprise a jaw member comprising an electrode, wherein the electrode is configured to supply energy from a power source to captured tissue. A control unit is configured to regulate the amount of energy delivered to the tissue through the monitoring of the current flowing through the tissue and the rate of change of the current flowing through the tissue. Through the monitoring of the current, the impedance of the tissue and the rate of change of impedance of the tissue may be determined to monitor the state of the captured tissue and reduce excess tissue heating.
