This transformer includes primary and secondary tracks (10, 20) that are coupled to one another by mutual inductance, the primary and secondary tracks being superimposed on top of each other in two parallel planes while being arranged to follow the same contour (C), the plane of the primary track corresponding to the main conductive layer of the circuit, said layer being deposited on a substrate (30), and the secondary track being supported, plumb with the primary track, by supporting means including walls (41-46; 51-56), each wall bearing directly on the substrate and against a lower surface (24) of the secondary track (20), and having a length (L) larger than a width (I), and having a height allowing a predetermined interval to be created between an upper surface (14) of the primary track (10) and the lower surface (24) of the secondary track (20).