Oscillator circuit

An oscillator circuit comprising:

• a current source including a plurality of MOS transistors;
• a resonant unit;
• an oscillation amplification unit connected to at least one first MOS transistor of the plurality of MOS transistors and connected in parallel to the resonant unit;
• a feedback resistor connected in parallel to the oscillation amplification unit;
• a switch unit having a first end connected to at least one second MOS transistor different from the first MOS transistor among the plurality of MOS transistors, and a second end connected to a connection point of the first MOS transistor and the oscillation amplification unit;
• and
• a level detecting unit detecting an input voltage of the oscillation amplification unit, and, when the detected input voltage is higher than a bias voltage level at a time of oscillation by an amount equal to or greater than a predetermined amount, or when the detected input voltage is lower than a bias voltage level at the time of the oscillation by an amount equal to or greater than a predetermined amount, outputs to the switch unit a control signal used to prevent a current from the second MOS transistor from flowing through the oscillation amplification unit, thereby preventing a voltage level of a connection point of the current source and the oscillation amplification unit from exceeding a breakdown voltage of the oscillation amplification unit.