The circuit device includes a first MOS transistor of a first conductivity type a source of which is coupled to a first power supply voltage node, a second MOS transistor of a second conductivity type a source of which is coupled to a second power supply voltage node, a first variable resistance circuit which is coupled between a drain of the first MOS transistor and an output node, and which includes a first switch, and a second switch coupled between the drain of the first MOS transistor and the second power supply voltage node. The control circuit performs control of making the first switch OFF and making the second switch ON when the clock signal fails to be output from the output node, and making the first switch ON and making the second switch OFF when the clock signal is output from the output node.

A circuit device includes an oscillation circuit configured to generate an oscillation signal, a first pre-driver disposed in a posterior stage of the oscillation circuit, a first output driver disposed in a posterior stage of the first pre-driver, a first regulator configured to supply a first regulated voltage to the first pre-driver, and a second regulator configured to supply a second regulated voltage to the first output driver, wherein the second regulator is shorter in transient response time than the first regulator.

A circuit device includes a first terminal to be coupled to one end of a resonator, a second terminal to be coupled to another end of the resonator, an amplifying element configured to amplify a signal from the first terminal to output the signal amplified to the second terminal, a first resistor element disposed on a signal path between an input node and an output node of the amplifying element, a capacitance element disposed on a signal path between the first terminal and the input node, and a first switch element configured to switch electrical coupling between the input node and a ground.

In an example, a system includes an oscillator circuit on a chip. The oscillator circuit includes a charging current generator including a current mirror, an amplifier, and an on-chip resistor, where the on-chip resistor is coupled to a pin on the chip. The oscillator circuit also includes oscillator circuitry coupled to the charging current generator, where the oscillator circuitry includes a comparator, a phase generator, a first capacitor coupled to a first resistor, and a second capacitor coupled to a second resistor. The system also includes an external resistor coupled to the pin, where the external resistor is external to the chip. The system includes an external capacitor coupled to the pin, where the external capacitor is external to the chip.

There is provided a semiconductor device comprising: a first inverter circuit (11) connected in parallel to a crystal vibrating element (X1); a second inverter circuit (12) connected to the first inverter circuit (11) so as to share an input therewith, and outputting an oscillation signal; and a wave filter (14) connected to the second inverter circuit (12) and having a passband that is determined in advance and includes an oscillation frequency of the oscillation signal.

A circuit device includes an oscillation circuit configured to generate an oscillation signal, a first pre-driver disposed in a posterior stage of the oscillation circuit, a first output driver disposed in a posterior stage of the first pre-driver, a first regulator configured to supply a first regulated voltage to the first pre-driver, and a second regulator configured to supply a second regulated voltage to the first output driver, wherein the second regulator is shorter in transient response time than the first regulator.

A circuit device includes a first terminal to be coupled to one end of a resonator, a second terminal to be coupled to another end of the resonator, an amplifying element configured to amplify a signal from the first terminal to output the signal amplified to the second terminal, a first resistor element disposed on a signal path between an input node and an output node of the amplifying element, a capacitance element disposed on a signal path between the first terminal and the input node, and a first switch element configured to switch electrical coupling between the input node and a ground.

A voltage-controlled oscillator includes a first transistor, a second transistor, a first center-tapped inductor, two first varactors, a second center-tapped inductor and two second varactors. The first and second transistors cooperatively forma cross-connected pair. The first center-tapped inductor and the first varactors cooperatively form a first LC tank. The second center-tapped inductor and the second varactors cooperatively forma second LC tank. The cross-connected pair is connected between the first and second LC tanks. The first and second center-tapped inductors are mutual-inductively coupled to each other. An oscillation signal pair is provided between the first LC tank and the cross-connected pair.

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 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.