A method of maintaining constant movement of a cutting blade of an ultrasonic waveguide includes the steps of providing an ultrasonic transducer operable to convert a received motional voltage into a movement of a cutting blade of an ultrasonic waveguide, a motional feedback circuit connected in a parallel configuration with the ultrasonic transducer, and a variable power source operable to apply a first voltage between a set of connection points to the parallel configuration. A feedback voltage measured from the motional feedback circuit is determined and an output of the power source is varied based upon the measured feedback voltage to result in a substantially constant feedback voltage and, thereby, maintain a substantially constant rate of movement of the cutting blade across a variety of cutting loads.