A VCO (voltage-controlled oscillator) includes: a resonant tank having a parallel connection of an inductor, a fixed capacitor, a variable capacitor, a first temperature compensating capacitor, and a second temperature compensating capacitor across a first node and a second node, and configured to establish an oscillation of a first oscillatory voltage at the first node and a second oscillatory voltage at the second node; and a regenerative network placed across the first node and the second node to provide energy to sustain the oscillation. The variable capacitor is controlled by a control voltage, the first temperature compensating capacitor is controlled by a first temperature tracking voltage of a positive temperature coefficient, and the second temperature compensating capacitor is controlled by a second temperature tracking voltage of a negative temperature coefficient.

Phase-locked loop circuitry generates an output signal based on transformer based voltage controlled oscillator (VCO) circuitry. The VCO circuitry includes upper band circuitry including first oscillation circuitry, a first harmonic filter circuitry coupled to the first oscillation circuitry, and a first selection transistor coupled to the first harmonic filter circuitry and a current source. The first harmonic filter circuitry filters the output signal. The lower band circuitry includes second oscillation circuitry, a second harmonic filter circuitry coupled to the second oscillation circuitry, and a second selection transistor coupled to the second harmonic filter circuitry and the current source. The second harmonic filter circuitry filters the output signal.

An integrated circuit includes at least two identical, synchronous and independent oscillator circuits that are coupled one to one in parallel with each other at homologous oscillating nodes of the respective oscillator circuits. The coupling in parallel is made using at least one coupling track that is configured so as to not introduce any phase shift or to introduce a very small phase shift.

A variable capacitor circuit includes a capacitor block including a first varactor element comprising a first transistor having a first size, a second varactor element comprising a second transistor having a second size different from the first size, a first terminal commonly connected to a source and a drain of the first transistor, a second terminal commonly connected to a source and a drain of the second transistor, and an RC circuit connected to a gate of the first transistor and a gate of the second transistor.

A system includes a data path and a phase-locked loop (PLL) coupled to the data path. The system also includes a voltage-controlled oscillator (VCO) coupled to the PLL. The VCO includes an LC circuit with first and second differential output terminals. The VCO also includes a first resistor coupled between the first differential output terminal and drain terminals of a first pair of complementary metal-oxide semiconductor (CMOS) transistors. The VCO also includes a second resistor coupled between the second differential output terminal and drain terminals of a second pair of CMOS transistors.

A voltage controlled oscillator includes a first inductor; a first variable capacitance unit including a first variable capacitance element having a variable capacitance and a second variable capacitance element having a variable capacitance; a first node configured for application of a first voltage to the first variable capacitance unit; a cross-coupled unit including a first transistor and a second transistor, an output of the first transistor connected to an input of the second transistor; a current source configured to flow a current through the first inductor, the first transistor, and the second transistor; a second variable capacitance unit including a third variable capacitance element having a variable capacitance, and a fourth variable capacitance element having a variable capacitance; and a second node different from the first node configured for application of a second voltage to the second variable capacitance unit.

Embodiments of the present disclosure may provide a circuit comprising a tank circuit. The tank circuit may include an inductor having a pair of terminals, a first pair of transistors, and a first pair of capacitors. Each transistor may be coupled between a respective terminal of the inductor and a reference voltage along a source-to-drain path of the transistor. Each capacitor may be provided in a signal path between an inductor terminal coupled to a respective first transistor in the first pair and a gate of a second transistor in the first pair.

An oscillator circuit includes a current source, an oscillating section, a first capacitor, and a setting section. The current source is coupled to a connection node, and is configured to cause a current having a current value based on an input voltage to flow from a first power node to the connection node. The oscillating section is provided on a current path between the connection node and a second power node. The oscillating section is configured to oscillate at an oscillation frequency based on a current flowing through the current path. The first capacitor is provided between the connection node and the second power node. The first capacitor has a capacitance that varies in accordance with a voltage at the connection node. The setting section is configured to perform variation operation on the basis of the voltage at the connection node. The variation operation is operation of varying an impedance between the connection node and the second power node.

A quadrature voltage-controlled oscillator circuit with phase shift includes two voltage-controlled oscillators with the same structure, wherein the two voltage-controlled oscillators are connected to each other through input and output ports, and the two voltage-controlled oscillators respectively include a cross-coupled oscillating circuit, an injection locking circuit, a resonant circuit and a voltage-controlled current source circuit which are electrically connected to each other; and signals are injected through the injection locking circuit and coupled with the oscillating circuit, so as to output a quadrature signal. An oscillator is enabled to operate stably in one mode by means of a simple circuit structure, and a good phase shift can be provided for the resonant circuit in a lower frequency band; and meanwhile, a tuning range of the oscillator is improved without increasing phase noise.

A system includes a data path and a phase-locked loop (PLL) coupled to the data path. The system also includes a voltage-controlled oscillator (VCO) coupled to the PLL. The VCO includes an LC circuit with first and second differential output terminals. The VCO also includes a first resistor coupled between the first differential output terminal and drain terminals of a first pair of complementary metal-oxide semiconductor (CMOS) transistors. The VCO also includes a second resistor coupled between the second differential output terminal and drain terminals of a second pair of CMOS transistors.