A first current source charges a capacitor. A second current source supplies a current to an input node of an inverter. A current mirror circuit has its output node coupled to an input node of the inverter. A resistor is coupled between the input node of the current mirror circuit and the capacitor.

A method for operating a fast start-up oscillator system, which includes a reference oscillator and a quartz oscillator connected to an electronic oscillator circuit, which is provided to supply a master clock signal to a start-up controller configured to perform a fast start-up procedure of the quartz oscillator via the reference oscillator. The start-up controller includes a calculation unit and a memory unit for storing data in connection with the reference oscillator for starting the quartz oscillator. The method includes parameterising the calculation unit for starting the quartz oscillator, generating excitation bursts, determining a phase deviation in different successive periods between the oscillation of the reference oscillator and the oscillation of the quartz oscillator, calculating a frequency error in the calculation unit, and correcting the frequency of the reference oscillator to the frequency of the quartz oscillator.