An electrosurgical generator is disclosed. The generator includes a microprocessor configured to generate a target impedance trajectory having at least one slope. The target impedance trajectory includes a plurality of target impedance values. The microprocessor is configured to drive tissue impedance along the target impedance trajectory by adjusting the output level to substantially match tissue impedance to a corresponding target impedance value. The microprocessor is further configured to compare tissue impedance to a threshold impedance value and adjust output of the electrosurgical generator when the tissue impedance is equal to or greater than the threshold impedance.