Abstract: According to the invention, the circuit comprises at least one two-port network of the "M-derived" section type and connected as an all-pass filter with a phase law which is a linear function of frequency. The two-port network is made in monolithic technology on gallium arsenide and the plane of its structure includes at least one elementary section, which, between an inlet and an outlet which are situated at a distance apart, is constituted by a spiral connected in parallel with a capacitor of metal-insulator-metal structure, with the mid point of the spiral being connected via another capacitor of metal-insulator metal structure to a ground plane. It is applicable to making transmission lines which are programamble in length.