[en] In JET, the feedback stabilisation of the plasma column in response to Vertical Displacement Events (VDEs) plays a key role in the operation of the machine. Presently, the Fast Radial Field Amplifier (FRFA) is composed of four inverter units each rated 2.5 kV, 2.5 kA at the output and based on GTO (Gate Turn-Off) thyristors, which can be configured to deliver either 10 kV, 2.5 kA or 5 kV, 5 kA on the load. The first configuration is preferred, as it provides a faster response thanks to the higher voltage available. After the EP2 enhancements, that will increase the heating power and will provide JET with an ITER like wall, ELMy H-mode scenarios, which are directly relevant for ITER, large Edge Localised Modes (ELMs) can occur that produce an excursion of the radial field in excess of the FRFA current/voltage capability, triggering a VDE that terminates the plasma. As a consequence, limits are set in the JET operational space at high current and high shaping. The importance of JET operation in this domain in view of ITER suggested an enhancement of the Vertical Stabilisation system, and in particular of the radial field amplifier current capability. This paper describes the conceptual design of a new radial field amplifier, named Enhanced Radial Field Amplifier (ERFA), aimed at increasing the output power with respect to the FRFA. The new system will provide 12 kV, 5 kA, so doubling the current swing and enhancing the voltage capability. The structure of ERFA is similar to FRFA: four distinct units are connected in series at the output to achieve the desired voltage level. However, the scheme of the single unit is different: it is composed of a step-down transformer, a single-quadrant ac/dc thyristor converter, a capacitor bank, a dc chopper to control the dc link voltage and a four-quadrant inverter. This scheme has been worked out on the basis of the availability of new power semiconductor components, able to provide faster switch-on and switch-off times and higher current capability with respect to the GTOs. After describing the new specifications required in terms of output currents, voltages and frequencies, the paper will describe the main design choices concerning the inverters, the dc choppers, the thyristor converters and the capacitor bank. The thermal analyses performed to identify the number of necessary H-bridges to be connected in parallel will be presented, together with the system simulations aimed at optimising the control strategies of the thyristor converters and of the dc choppers and verifying the design of the system. Finally, some hints regarding the control system will be given, with particular reference to the inverters. (author)