A circuit device includes an oscillation circuit configured to cause a resonator to oscillate, a clock signal output circuit configured to output a clock signal based on an oscillation signal from the oscillation circuit, a temperature compensation circuit configured to perform temperature compensation on an oscillation frequency of the oscillation signal, a low-potential-side power supply pad to which low-potential-side electric power is supplied, a high-potential-side power supply pad to which high-potential-side electric power is supplied, and an inter-power-supply capacitor provided between a low-potential-side power supply line electrically continuous with the low-potential-side power supply pad and a high-potential-side power supply line electrically continuous with the high-potential-side power supply pad. The inter-power-supply capacitor is formed of at least two metal layers provided in a region where the temperature compensation circuit is disposed in a plan view.

A stacked synthesizer for wide local oscillator (LO) generation using a dynamic divider. The phase locked loop can include a plurality of voltage controlled oscillators (VCOs), and a selector that can be configured to select an output of one of the plurality of VCOs. The selected output of one of the plurality of VCOs can be provided to an on-chip dynamic divider and to an off-chip dynamic divider for LO sharing. The dynamic dividers can be configured to generate synthesizer outputs based on a multiplication of the selected output of one of the plurality of VCOs by a factor (1+1/M), where M is a variable number.

A crystal oscillator includes a crystal resonator; an inverting amplifier configured to be coupled between a pair of excitation electrodes of the crystal resonator; and a control circuit configured to initiate an alarm and raise gain of the inverting amplifier in a case where an index value for representing oscillation amplitude of the crystal resonator in an oscillation state is equal to or lower than a reference value.

In an example, a voltage-controlled oscillator (VCO) includes: an oscillator having a supply input; and a voltage regulator, coupled to the supply input. The voltage regulator includes: a first transistor and a second transistor providing a first source-coupled transistor pair, and a third transistor and a fourth transistor providing a second source-coupled transistor pair; an active load coupled to drains of the first, second, third, and fourth transistors; a first current source coupled to sources of the first and second transistors, and a second current source coupled to sources of the third and fourth transistors; a fifth transistor having a source and a drain coupled to the source and the drain, respectively, of the first transistor; and a sixth transistor having a source and a drain coupled to the source and the drain, respectively, of the third transistor.

A crystal oscillator device is disclosed. The crystal oscillator device includes: a casing; a crystal piece provided in the casing; a pair of excitation electrodes provided on the crystal piece; a magnetic flux generating member provided on the crystal piece; a coil through which magnetic flux from the magnetic flux generating member passes; and an alarm generator configured to generate an alarm based on a signal whose amplitude is equal to or less than a reference value, the signal being generated in the coil.

A crystal oscillator device is disclosed. The crystal oscillator device includes: a crystal piece provided in a casing; a pair of excitation electrodes provided on the crystal piece; a light emitting element configured to emit light that is to be reflected by one of the excitation electrodes to generate reflected light; a light receiving element configured to receive the reflected light; and an alarm generator configured to generate an alarm based on a signal upon an index value being less than or equal to a reference value, the signal being generated in the light receiving element, the index value representing an oscillation level of the crystal piece in an oscillating state.

A crystal oscillator device is disclosed. The crystal oscillator device includes: a crystal oscillator including a casing, a crystal piece, a pair of excitation electrodes configured to excite a main vibration, and a pair of sub vibration electrodes configured to excite a sub-vibration; and an alarm generator configured to generate an alarm based on a signal whose amplitude is equal to or less than a reference value, the signal being generated in the sub vibration electrodes.

A crystal oscillator device is disclosed. The crystal oscillator device includes a casing; a crystal piece; a pair of excitation electrodes; a transmission antenna electrically coupled to one of the excitation electrodes; a reception antenna configured to receive a radio wave from the transmission antenna; and an alarm generator configured to generate an alarm based on a signal whose amplitude is equal to or less than a reference value, the signal being received by the reception antenna.

A crystal oscillator device is disclosed. The crystal oscillator device includes a crystal piece provided in a casing; a pair of excitation electrodes provided for the crystal piece; a coil provided on the crystal piece; a magnetic flux generating member configured to generate magnetic flux passing through the coil; and an alarm generator configured to generate an alarm based on a signal whose amplitude is equal to or less than a reference value, the signal being generated in the coil.

A circuit device includes an oscillation circuit configured to cause a resonator to oscillate, a clock signal output circuit configured to output a clock signal based on an oscillation signal from the oscillation circuit, a temperature compensation circuit configured to perform temperature compensation on an oscillation frequency of the oscillation signal, a low-potential-side power supply pad to which low-potential-side electric power is supplied, a high-potential-side power supply pad to which high-potential-side electric power is supplied, and an inter-power-supply capacitor provided between a low-potential-side power supply line electrically continuous with the low-potential-side power supply pad and a high-potential-side power supply line electrically continuous with the high-potential-side power supply pad. The inter-power-supply capacitor is formed of at least two metal layers provided in a region where the temperature compensation circuit is disposed in a plan view.