The resonant device comprises an electromechanical resonator of nanometric or micrometric size that comprises a mobile element and a fixed element. Detection means provide detection signals representative of movement of the mobile element with respect to the fixed element to a feedback loop that is connected to an excitation input of the resonator. The resonator is formed on the same substrate as the detection means and feedback loop. The feedback loop comprises at most first and second transistors connected in series between a reference voltage and the excitation terminal. A capacitive load is connected between the excitation terminal and reference voltage. The detection signals control the conductivity of the first transistor.