International audienceThis work presents some results in connection with the amplifier limitation mechanisms in quartz crystal oscillators. These mechanisms were studied using the so called non linear dipolar method. This technique makes it possible to determine the close-loop operating conditions of the oscillator using open loop transient analyses. The well understanding of these limitation mechanisms should allow us to custom made quartz crystal oscillators, specifically for metrology and space applications. Key words: Dipolar method, dipolar impedance, quartz crystal oscillator, high-Q factor, time-domain analysis, SPICE