An oscillator circuit comprises a crystal oscillator arranged to generate an oscillation signal, a bias current generator arranged to supply a bias current to the crystal oscillator, and a feedback stage arranged to generate a feedback signal in response to an amplitude of the oscillation signal reaching an amplitude threshold. The bias current generator is arranged to: in response to a supply of power to the oscillator circuit being switched on, generate the bias current at an increasing level commencing from a first level; in response to the feedback signal, terminate the increasing; and during subsequent oscillation of the crystal oscillator, supply the bias current at a second level dependent on a final level of the bias current reached when the increasing is terminated.

An oscillator circuit comprises a crystal oscillator arranged to generate an oscillation signal, a bias current generator arranged to supply a bias current to the crystal oscillator, and a feedback stage arranged to generate a feedback signal in response to an amplitude of the oscillation signal reaching an amplitude threshold. The bias current generator is arranged to: in response to a supply of power to the oscillator circuit being switched on, generate the bias current at an increasing level commencing from a first level; in response to the feedback signal, terminate the increasing; and during subsequent oscillation of the crystal oscillator, supply the bias current at a second level dependent on a final level of the bias current reached when the increasing is terminated.

An oscillation circuit includes a first oscillation circuit configured to oscillate a resonator to generate a first oscillation signal, a second oscillation circuit configured to generate a second oscillation signal, a frequency measurement circuit configured to measure a frequency of the second oscillation signal based on the first oscillation signal in a first period in which the first oscillation circuit is in operation, a holding circuit configured to hold a measurement result by the frequency measurement circuit in a second period in which the first oscillation circuit is not in operation, and an oscillation signal generation circuit configured to generate a third oscillation signal based on the second oscillation signal and the measurement result held in the holding circuit in a third period in which the first oscillation circuit starts up, wherein the third oscillation signal is supplied to the first oscillation circuit in the third period.

An oscillation circuit includes a first oscillation circuit configured to oscillate a resonator to generate a first oscillation signal, a second oscillation circuit configured to generate a second oscillation signal, a frequency measurement circuit configured to measure a frequency of the second oscillation signal based on the first oscillation signal in a first period in which the first oscillation circuit is in operation, a holding circuit configured to hold a measurement result by the frequency measurement circuit in a second period in which the first oscillation circuit is not in operation, and an oscillation signal generation circuit configured to generate a third oscillation signal based on the second oscillation signal and the measurement result held in the holding circuit in a third period in which the first oscillation circuit starts up, wherein the third oscillation signal is supplied to the first oscillation circuit in the third period.

A ring voltage controlled oscillator (VCO) circuit is herein provided. According to one embodiment, a ring VCO circuit includes a plurality of stages connected in series, wherein each stage includes a first inverter, a second inverter, a third inverter and a fourth inverter, the first inverter connected in parallel with the third and fourth inverters and the second inverter connected in parallel with the third and fourth inverters, and a first biasing resistor connected to a first node and coupled to an input of the first inverter. The first biasing resistor includes a first switch configured to set the first biasing resistor to about zero voltage.

A ring voltage controlled oscillator (VCO) circuit is herein provided. According to one embodiment, a ring VCO circuit includes a plurality of stages connected in series, wherein each stage includes a first inverter, a second inverter, a third inverter and a fourth inverter, the first inverter connected in parallel with the third and fourth inverters and the second inverter connected in parallel with the third and fourth inverters, and a first biasing resistor connected to a first node and coupled to an input of the first inverter. The first biasing resistor includes a first switch configured to set the first biasing resistor to about zero voltage.

A clock generation circuit includes a switched capacitor circuit for providing a discrete amount of charge to a resonator for sustaining energization of the resonator at specific portions of the clock cycle.

An electronic device comprises a regulator, and an oscillator and a resistor coupled to the regulator. The electronic device further comprises a feedback controller that includes a differential amplifier coupled between the oscillator, the resistor, and the regulator. The feedback controller is configured to apply a control voltage to the regulator in response to a resistor voltage upon the resistor and an oscillator voltage upon the oscillator. The feedback controller can be coupled to control a substantially equal voltage upon the resistor and the oscillator.

Methods and apparatus generate an oscillating output signal having a voltage swing greater than a voltage swing across nodes of active devices. An example oscillator includes a tank to generate an oscillating output signal in response receiving an edge of an enable signal; a feedback generator including a first gain stage forming a first feedback loop with the tank, the first feedback loop providing a first charge to maintain the oscillating output signal and a second gain stage forming a second feedback loop with the tank, the second feedback loop providing a second charge to maintain the oscillating output signal, the first and second charges combining with the oscillating output signal to generate a high voltage swing; and an attenuator connected between the tank and the feedback generator to isolate the tank from active components of the feedback generator.

Methods and apparatus generate an oscillating output signal having a voltage swing greater than a voltage swing across nodes of active devices. An example oscillator includes a tank to generate an oscillating output signal in response receiving an edge of an enable signal; a feedback generator including a first gain stage forming a first feedback loop with the tank, the first feedback loop providing a first charge to maintain the oscillating output signal and a second gain stage forming a second feedback loop with the tank, the second feedback loop providing a second charge to maintain the oscillating output signal, the first and second charges combining with the oscillating output signal to generate a high voltage swing; and an attenuator connected between the tank and the feedback generator to isolate the tank from active components of the feedback generator.