Patent ID: 8333778

Claim:
An ultrasonic surgical assembly, comprising: an ultrasonic transducer operable to convert a received motional voltage into a movement of a cutting blade of an ultrasonic waveguide; a first capacitive element in a series configuration with the ultrasonic transducer; a motional feedback circuit connected in a parallel configuration with the ultrasonic transducer and comprising a second capacitive element and a third capacitive element in a series configuration with each other and, together, connected in a parallel configuration with the series configuration of the ultrasonic transducer and the first capacitive element, a capacitive value of the third capacitive element being a fraction of a capacitive value of the ultrasonic transducer, the fraction having a value less than one, a capacitive value of the second capacitive element being a capacitive value of the first capacitive element multiplied by the fraction; a variable power source operable to apply a first voltage between a set of connection points to the parallel configuration; a voltage meter operable to determine a feedback voltage measured from the motional feedback circuit; and a voltage controller operable to vary an output of the power source based upon the measured feedback voltage, resulting in a substantially constant feedback voltage and maintaining a substantially constant rate of movement of the cutting blade across a variety of cutting loads.