A surgical instrument comprising: (a) a shaft; (b) an ultrasonic transducer; (c) a waveguide acoustically coupled with the ultrasonic transducer and extending distally through the shaft; (d) an end effector arranged at a distal end of the shaft, wherein the end effector comprises: (i) an ultrasonic blade acoustically coupled with the waveguide, wherein the ultrasonic transducer is operable to drive the waveguide and the ultrasonic blade with ultrasonic energy, (ii) a clamp arm movable relative to the ultrasonic blade for clamping tissue therebetween, and (iii) anRF electrode (42, 44) operable to seal tissue with RF energy; (e) an ultrasonic electrical circuit operable to energize the ultrasonic transducer, wherein the ultrasonic electrical circuit includes an active path and a return path; and (f) an RF electrical circuit operable to deliver RF energy to the RF electrode, wherein the RF electrical circuit includes an active path and a return path, wherein the return path of the ultrasonic electrical circuit passes through an electrically conductive element, wherein the return path of the RF electrical circuit passes through the electrically conductive element; wherein the return path of the ultrasonic electrical circuit and the return path of the RF electrical circuit pass through the ultrasonic transducer; wherein the ultrasonic transducer comprises: (i) a proximal end element, (ii) a distal end element, (iii) a piezoelectric element disposed between the proximal end element and the distal end element, and (iv) a transducer electrode coupled to the piezoelectric element, wherein the return path of the ultrasonic electrical circuit and the return path of the RF electrical circuit both pass through the transducer electrode. (a) a shaft; (b) an ultrasonic transducer; (c) a waveguide acoustically coupled with the ultrasonic transducer and extending distally through the shaft; (d) an end effector arranged at a distal end of the shaft, wherein the end effector comprises: (i) an ultrasonic blade acoustically coupled with the waveguide, wherein the ultrasonic transducer is operable to drive the waveguide and the ultrasonic blade with ultrasonic energy, (ii) a clamp arm movable relative to the ultrasonic blade for clamping tissue therebetween, and (iii) anRF electrode (42, 44) operable to seal tissue with RF energy; (i) an ultrasonic blade acoustically coupled with the waveguide, wherein the ultrasonic transducer is operable to drive the waveguide and the ultrasonic blade with ultrasonic energy, (ii) a clamp arm movable relative to the ultrasonic blade for clamping tissue therebetween, and (iii) anRF electrode (42, 44) operable to seal tissue with RF energy; (e) an ultrasonic electrical circuit operable to energize the ultrasonic transducer, wherein the ultrasonic electrical circuit includes an active path and a return path; and (f) an RF electrical circuit operable to deliver RF energy to the RF electrode, wherein the RF electrical circuit includes an active path and a return path, (i) a proximal end element, (ii) a distal end element, (iii) a piezoelectric element disposed between the proximal end element and the distal end element, and (iv) a transducer electrode coupled to the piezoelectric element,