Oscillator circuit with an inverter amplifier having reduced consumption

Inverter oscillator circuit (10) for delivering an alternating output signal (SOSC), this inverter oscillator circuit (10) including a parallel arrangement, between an input terminal (A) and an output terminal (B), of an inverter amplifier means (2, 3), a resonator (1) and a resistor (4), first and second load capacitors (5, 6) being respectively connected between said input and output terminals (A, B), on the one hand, and a supply potential (VSS, VDD, VR), on the other hand,

• said resonator being a quartz resonator having a first undesired vibration mode at a first frequency and a second desired vibration mode at a second frequency,
• wherein said inverter oscillator circuit (10) further includes:
• control means (7a, 7b, 8) for controlling said inverter amplifier means (2, 3) such that it has a so-called start-up transconductance value (Gm) during a start-up phase and a so-called reduced transconductance value (gm), lower than said start-up transconductance value (Gm), in steady state at the end of said start-up phase;
• and
• means (9, 90) for smoothing an amplitude decrease in the output signal (SOSC) resulting from the passage of said start-up transconductance value (Gm) to said reduced transconductance value (gm),
• said start-up transconductance value (Gm) being determined such that the resonator (1) is set into vibration according to said second desired vibration mode during said start-up phase, and said reduced transconductance value (gm) is determined such that the resonator continues to vibrate according to the second desired vibration mode in steady state.

Method for maintaining the vibrations of a resonator (1) and generating an alternating output signal (SOSC) by means of an inverter oscillator circuit (10) including an inverter amplifier means (2, 3), this resonator (1) having a first undesired vibration mode at a first frequency and a second desired vibration mode at a second frequency,

• this method including
• a start-up step consisting in controlling said inverter amplifier means (2, 3) such that it has a so-called start-up transconductance value (Gm) during said start-up step, this start-up transconductance value (Gm) being determined such that said resonator (1) is set into vibration according to the desired vibration mode;
• and
• a switching step consisting in controlling said inverter amplifier means (2, 3) such that it has a so-called reduced transconductance value (gm) lower than said start-up transconductance value (Gm) as soon as said resonator (1) is in steady state.