A resonant circuit to be connected to a negative resistance unit is disclosed. The resonant circuit includes a pair of resonant transmission lines electrically coupled to each other and a coupling transmission line connecting the resonant transmission lines. The resonant transmission lines and the coupling transmission line are formed on a semiconductor substrate. The resonant transmission lines have a length corresponding to a quarter wavelength (/4) of twice of the resonant frequency attributed to the resonant circuit.

A resonant circuit to be connected to a negative resistance unit is disclosed. The resonant circuit includes a pair of resonant transmission lines electrically coupled to each other and a coupling transmission line connecting the resonant transmission lines. The resonant transmission lines and the coupling transmission line are formed on a semiconductor substrate. The resonant transmission lines have a length corresponding to a quarter wavelength (/4) of twice of the resonant frequency attributed to the resonant circuit.

An oscillator circuit topology using a one-pin external resonator suitable for integrated-circuit low-voltage, low-power applications that require a fast-starting accurate clock is disclosed. The circuit incorporates a novel arrangement of a plurality of active transconductance cells that respond to a digital control and provide adjustable loop gain for the oscillator. A programmable number of start-up transconductance cells are engaged in the initial phase of the oscillation for temporarily increasing the loop gain and energizing the resonator, and are disengaged from the oscillator core once the oscillation level is sufficiently large. The start-up transconductance cells may be identical to the always-on transconductance cells in the oscillator core, or they may be scaled versions of those cells. In addition, a programmable number of identical or scaled transconductance cells may be provided in the oscillator core itself, for accommodating different resonators. Internal circuit implementations of the transconductance cells that enable their efficient combination for increasing the oscillator loop gain are also disclosed.

An oscillator circuit topology using a one-pin external resonator suitable for integrated-circuit low-voltage, low-power applications that require a fast-starting accurate clock is disclosed. The circuit incorporates a novel arrangement of a plurality of active transconductance cells that respond to a digital control and provide adjustable loop gain for the oscillator. A programmable number of start-up transconductance cells are engaged in the initial phase of the oscillation for temporarily increasing the loop gain and energizing the resonator, and are disengaged from the oscillator core once the oscillation level is sufficiently large. The start-up transconductance cells may be identical to the always-on transconductance cells in the oscillator core, or they may be scaled versions of those cells. In addition, a programmable number of identical or scaled transconductance cells may be provided in the oscillator core itself, for accommodating different resonators. Internal circuit implementations of the transconductance cells that enable their efficient combination for increasing the oscillator loop gain are also disclosed.

Embodiments can provide individualized controlling of noise injection during startup of a crystal oscillator. In some embodiments, a simple learning block can be placed in parallel to a oscillator circuit to control noise injection during the startup of the crystal oscillator. The learning block can be configured to control the noise injection during the startup of the crystal oscillator by determining whether the crystal oscillator has been stabilized. In some embodiments, an adjustment block may be employed to adjust the count determined by the learning block based on one or more measured characteristics of the crystal oscillator during a startup of the crystal oscillator. In some embodiments, a simple block that creates a negative capacitance can be configured in parallel to the crystal oscillator.

Embodiments can provide individualized controlling of noise injection during startup of a crystal oscillator. In some embodiments, a simple learning block can be placed in parallel to a oscillator circuit to control noise injection during the startup of the crystal oscillator. The learning block can be configured to control the noise injection during the startup of the crystal oscillator by determining whether the crystal oscillator has been stabilized. In some embodiments, an adjustment block may be employed to adjust the count determined by the learning block based on one or more measured characteristics of the crystal oscillator during a startup of the crystal oscillator. In some embodiments, a simple block that creates a negative capacitance can be configured in parallel to the crystal oscillator.

A crystal oscillator circuit is provided. The crystal oscillator circuit includes an oscillator start-up circuit having a first output terminal and a second output terminal, where the second output terminal outputs a first oscillation signal; and a waveform conversion circuit configured to convert the first oscillation signal to a rectangular wave signal. The crystal oscillator circuit also includes a first current source configured to output a first current to drive the oscillator start-up circuit; and a second current source configured to output a second current, and being connected in parallel with the first current source to jointly drive the oscillator start-up circuit. Further the crystal oscillator circuit includes a pulse generation circuit configured to generate a control pulse signal to control the second current source to output the second current after power on and to stop outputting the second current after a preset time.

A crystal oscillator circuit is provided. The crystal oscillator circuit includes an oscillator start-up circuit having a first output terminal and a second output terminal, where the second output terminal outputs a first oscillation signal; and a waveform conversion circuit configured to convert the first oscillation signal to a rectangular wave signal. The crystal oscillator circuit also includes a first current source configured to output a first current to drive the oscillator start-up circuit; and a second current source configured to output a second current, and being connected in parallel with the first current source to jointly drive the oscillator start-up circuit. Further the crystal oscillator circuit includes a pulse generation circuit configured to generate a control pulse signal to control the second current source to output the second current after power on and to stop outputting the second current after a preset time.

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.