An electrosurgical generator comprising: an electromagnetic signal supply unit for generating EM energy; an electrical signal supply unit for generating an electrical signal for driving a magnetostrictive ultrasound transducer; an output port configured to be connectable to an electrosurgical instrument for delivering the EM energy from a distal end thereof and for generating ultrasonic vibrations using the electrical signal; and a feed structure for conveying the EM energy from the EM signal supply unit to the output port, and for conveying the electrical signal from the electrical signal supply unit to the output port, wherein the feed structure has a common signal pathway for conveying the EM energy and the electrical signal to the output port wherein the electrical signal supply unit comprises: a first power supply for outputting a first supply signal and a second supply signal; a signal source for outputting a first control signal and a second control signal; a first switching circuit having a control input coupled to the signal source for receiving the first control signal, a supply input coupled to the first power supply for receiving the first supply signal, and an output, wherein the first switching circuit is operable to provide at the output at least part of the electrical signal based on the first supply signal and the first control signal; a second switching circuit having a control input coupled to the signal source for receiving the second control signal, a supply input coupled to the second power supply for receiving the second supply signal, and an output, wherein the second switching circuit is operable to provide at the output a second part of the electrical signal based on the second supply signal and the second control signal, and a common signal pathway coupled the output of the first switching circuit for receiving a first part of the electrical signal, and coupled to the output of the second switching circuit for receiving the second part of the electrical signal, and for combining the first and second parts to form the electrical signal. an electromagnetic signal supply unit for generating EM energy; an electrical signal supply unit for generating an electrical signal for driving a magnetostrictive ultrasound transducer; an output port configured to be connectable to an electrosurgical instrument for delivering the EM energy from a distal end thereof and for generating ultrasonic vibrations using the electrical signal; and a feed structure for conveying the EM energy from the EM signal supply unit to the output port, and for conveying the electrical signal from the electrical signal supply unit to the output port, wherein the feed structure has a common signal pathway for conveying the EM energy and the electrical signal to the output port wherein the electrical signal supply unit comprises: a first power supply for outputting a first supply signal and a second supply signal; a signal source for outputting a first control signal and a second control signal; a first switching circuit having a control input coupled to the signal source for receiving the first control signal, a supply input coupled to the first power supply for receiving the first supply signal, and an output, wherein the first switching circuit is operable to provide at the output at least part of the electrical signal based on the first supply signal and the first control signal; a second switching circuit having a control input coupled to the signal source for receiving the second control signal, a supply input coupled to the second power supply for receiving the second supply signal, and an output, wherein the second switching circuit is operable to provide at the output a second part of the electrical signal based on the second supply signal and the second control signal, and a common signal pathway coupled the output of the first switching circuit for receiving a first part of the electrical signal, and coupled to the output of the second switching circuit for receiving the second part of the electrical signal, and for combining the first and second parts to form the electrical signal. a first power supply for outputting a first supply signal and a second supply signal; a signal source for outputting a first control signal and a second control signal; a first switching circuit having a control input coupled to the signal source for receiving the first control signal, a supply input coupled to the first power supply for receiving the first supply signal, and an output, wherein the first switching circuit is operable to provide at the output at least part of the electrical signal based on the first supply signal and the first control signal; a second switching circuit having a control input coupled to the signal source for receiving the second control signal, a supply input coupled to the second power supply for receiving the second supply signal, and an output, wherein the second switching circuit is operable to provide at the output a second part of the electrical signal based on the second supply signal and the second control signal, and a common signal pathway coupled the output of the first switching circuit for receiving a first part of the electrical signal, and coupled to the output of the second switching circuit for receiving the second part of the electrical signal, and for combining the first and second parts to form the electrical signal.