A handheld electrosurgical instrument includes a handpiece (2) and an electrode assembly (3), the electrode assembly including one or more electrodes (12), (13) and a connector (8), (9) by which the electrode assembly (3) is capable of being attached and detached with respect to the handpiece (2). The handpiece includes a battery (4), an RF oscillator circuit (30) for generating a radio frequency output, an RF output circuit (5) and switching means (7) operable by a user of the electrosurgical instrument. A control circuit is provided (6) for controlling the RF output, the control circuit (6) being capable of receiving signals from the switching means (7) and causing one or more RF outputs to be supplied to the electrode assembly (3) in response thereto. The RF output circuit includes a transformer including at least one primary winding (14) and a plurality of secondary windings (15), (16), (17). The connector on the electrode assembly (9) includes a component (29) capable of physically selecting a particular secondary winding or combination of secondary windings so as to modify the RF output reaching the one or more electrodes.
