A clock oscillator includes with a pullable BAW oscillator to generate an output signal with a target frequency. The BAW oscillator is based on a BAW resonator and voltage-controlled variable load capacitance, responsive to a capacitance control signal to provide a selectable load capacitance. An oscillator driver (such as a differential negative gm transconductance amplifier), is coupled to the BAW oscillator to provide an oscillation drive signal. The BAW oscillator is responsive to the oscillation drive signal to generate the output signal with a frequency based on the selectable load capacitance. The oscillator driver can include a bandpass filter network with a resonance frequency substantially at the target frequency.

A circuit device includes an oscillation signal generation circuit that generates an oscillation signal by using a resonator and a processing circuit that estimates an aging characteristic of the oscillation frequency of the resonator based on the result of comparison between the phase of a reference signal based on a satellite signal transmitted from a navigation satellite and the phase of a clock signal based on the oscillation signal. The processing circuit estimates the aging characteristic based on an index value representing the reliability of the state of the received satellite signal and the result of the phase comparison.

A resonator device includes a first resonator that generates a reference clock signal, a second resonator that generates a first clock signal having a frequency adjusted based on the reference clock signal, and a circuit device that includes a temperature sensor for performing temperature compensation on an oscillation frequency of the first resonator. The temperature sensor is disposed on the circuit device such that the first resonator overlaps the temperature sensor in a plan view.

A resonator device includes first and second resonators and an integrated circuit. The integrated circuit includes first and second oscillation circuits that oscillate first and second resonators, first and second terminals connected to the first oscillation circuit, and third and fourth terminals connected to the second oscillation circuit. The first terminal of the integrated circuit and one electrode of the first resonator are connected to each other via a bump. The third terminal and one electrode of the second resonator are connected to each other via a bump. In a plan view, at least a portion of the first resonator overlaps the first oscillation circuit and at least a portion of the second resonator overlaps the second oscillation circuit.

An oscillator includes a resonator, a circuit device that is electrically coupled to the resonator and generates a clock signal, and an output terminal that is electrically coupled to the circuit device and outputs the clock signal. The circuit device includes an abnormality detection circuit, and when an abnormal state is detected by the abnormality detection circuit, the circuit device changes a signal characteristic of the clock signal.

An oscillator includes a resonator, a circuit device that is electrically coupled to the resonator and generates a clock signal, a control terminal that is electrically coupled to the circuit device, and an output terminal that is electrically coupled to the circuit device and outputs the clock signal. The circuit device includes an abnormality detection circuit and sets a potential of the control terminal to an abnormality detection voltage when an abnormal state is detected by the abnormality detection circuit.

A circuit device includes an oscillation signal generation circuit that generates an oscillation signal by using a resonator and a processing circuit that estimates an aging characteristic of the oscillation frequency of the resonator based on the result of comparison between the phase of a reference signal based on a satellite signal transmitted from a navigation satellite and the phase of a clock signal based on the oscillation signal. The processing circuit estimates the aging characteristic based on an index value representing the reliability of the state of the received satellite signal and the result of the phase comparison.

A crystal oscillator including a feedback circuit, and a reference clock generating circuit including the crystal oscillator. The crystal oscillator is configured to generate an oscillating signal based on a natural frequency of a crystal. The crystal oscillator may include: a current generating circuit connected to a first node having a first voltage and a second node having a second voltage, and configured to output a first current to the second node; a feedback circuit connected to the generating circuit via the first and second nodes and configured to adjust a level of the second voltage by controlling a level of the first voltage; and a crystal circuit connected to the second node and configured to generate the oscillating signal based on the second voltage.

An output buffer circuit includes an output node, a P-type transistor, an N-type transistor, and a first variable resistor circuit provided in a signal path between a drain of one of the P-type transistor and the N-type transistor and the output node.

An oscillator includes a resonator, an oscillation circuit, and first and temperature compensation circuits. The first temperature compensation circuit performs a first-order first temperature compensation processing in a first mode and performs the first-order first temperature compensation processing and a high-order first temperature compensation processing in a second mode for a frequency of a first clock signal generated by oscillation of the resonator by the oscillation circuit. The second temperature compensation circuit receives the first clock signal and outputs a second clock signal subjected to a high-order second temperature compensation processing based on the first clock signal.