An oscillator including two groups of elementary junctions having giant magnetoresistance effect traversed by electric currents, the junctions of each of the two groups being in series and energized by respective main currents and the voltages across the terminals of the groups being added together to provide a voltage on an output of the oscillating circuit. The voltage across the terminals of one or more junctions of a first group is applied to a first input of a phase comparator and the voltage across the terminals of one or more junctions of the other group is applied to another input of the phase comparator, the phase comparator providing on two outputs secondary currents of the same amplitude and of opposite signs, which are dependent on the mean phase difference between the voltages applied to the inputs, the secondary currents each being added to a respective main current.