An electrosurgical instrument in which an amplifier for getting microwave power is located in the same region at a radiating structure for delivering that power in a distal portion of the instrument. The instrument may be insertable through the instrument channel of a surgical scoping device, e.g. endoscope. The entire microwave generating line up may be incorporated into the instrument so that only DC input power is needed. The microwave power losses and associated drawbacks present in known devices can therefore be avoided. The amplifier may be fabricated using wide band-gap semiconductor materials, such as GaN and GaN-based alloys, which offer the ability to fabricate devices that are active at RF and microwave frequencies.
