The invention relates to a thermal treatment applicator (19) for the deposition of thermal energy within tissue of a body (10) of a patient. The applicator (19), comprises: a plurality of RF antennae (20) for radiating a RF electromagnetic field toward the body (10)；—a plurality of RF power amplifiers (21) supplying RF signals to the RF antennae (20), wherein each RF power amplifier (21) comprises a transistor and an output matching network (22) transforming the output impedance of the transistor into a low impedance value. Moreover, the invention relates to a MR imaging guided therapy system (1).
