Apparatus, circuits and methods for clock generation are disclosed herein. In some embodiments, an apparatus is disclosed. The apparatus includes: a first transistor pair electrically coupled to a pair of output nodes; a second transistor pair electrically coupled to the pair of output nodes; and an inductive unit electrically coupled between the output nodes and electrically coupled between gates of the first transistor pair. The inductive unit comprises: a first inductive element electrically coupled to one gate of the first transistor pair; and a second inductive element electrically coupled to one of the output nodes. The first inductive element and the second inductive element are configured to be magnetically coupled to each other.

In some embodiments, a differential oscillator includes a differential circuit coupled between a first output node and a second output node and a transformer-coupled band-pass filter (BPF). The transformer-coupled BPF is coupled between the first output node and the second output node and includes a coupling device and a transformer. The coupling device is coupled between the first output node and the second output node. The transformer includes a first winding coupled between the first output node and a voltage node and a second winding coupled between the second output node and the voltage node.

Apparatus, circuits and methods for clock generation are disclosed herein. In some embodiments, an apparatus is disclosed. The apparatus includes: a first transistor pair electrically coupled to a pair of output nodes; a second transistor pair electrically coupled to the pair of output nodes; and an inductive unit electrically coupled between the output nodes and electrically coupled between gates of the first transistor pair. The inductive unit comprises: a first inductive element electrically coupled to one gate of the first transistor pair; and a second inductive element electrically coupled to one of the output nodes. The first inductive element and the second inductive element are configured to be magnetically coupled to each other.

A variable reactance apparatus, tunable oscillator and method for changing a gain associated with an input signal of a tunable oscillator are disclosed. An embodiment of the variable reactance apparatus includes a plurality of unit variable reactance structures including respective control input nodes, and a control circuit configured to connect each of the control input nodes to a respective signal from among a plurality of signals including a first tuning signal and a second tuning signal. An embodiment of a tunable oscillator includes a resonance circuit, a negative impedance structure and a variable reactance apparatus configured for tuning of the oscillator. An embodiment of a method includes altering connections of first and second tuning signals to control input nodes of respective first and second sets of unit variable reactance structures while holding constant a sum of the number of unit variable reactance structures in the first and second sets.

A frequency variable oscillator generates a clock having a frequency according to a control signal. A reference current source generates a reference current. A path selector distributes the reference current to a first path and a second path in a time-sharing manner in synchronization with the clock. An F/V conversion circuit includes a capacitor connected to the first path, and charges or discharges the capacitor with the reference current and generates a detection voltage. The reference voltage source includes a resistor connected to the second path, and outputs a reference voltage according to a voltage across the resistor. A feedback circuit adjusts a control signal so that the detection voltage approaches the reference voltage.

A voltage controlled oscillator (VCO) circuit employing digital amplitude control of the output oscillating signal and method of operation. The digital control is provided by an analog to digital converter (ADC) element that is shared among many other operating blocks in a system. In a configuration, the oscillator current is obtained by implementing transistors in a linear region and controlling them digitally. The optimum amplitude detection is performed by measuring the DC voltage at the common mode nodes in the oscillator, and is realized using reduced time compared to an extensive frequency measurement over a long time window. The digital control is implemented using an on-chip regulator, and employs digital controls for adjusting the current consumption which leads to low on-chip area overhead, low cost, and a scalable implementation. In an implementation, a one-time code can be obtained for optimum phase noise operation when providing the digital amplitude control.

The present technology relates to a DAC (Digital to Analog Converter) and an oscillation circuit that allow widening of a range of a voltage to be output from the DAC. A plurality of first switches is connected to a voltage-dividing resistor and each configured to output, as a first voltage, a voltage at a corresponding one of connection points between the voltage-dividing resistor and the plurality of first switches. A plurality of second switches is connected to the voltage-dividing resistor and each configured to output, as a second voltage, a voltage at a corresponding one of connection points between the voltage-dividing resistor and the plurality of second switches. The present technology can be applied to, for example, a VCO (Voltage-Controlled Oscillator) and the like that oscillates a signal with a frequency according to a voltage to be output from a DAC.

A band-pass filter (BPF) includes a pair of coupled transformers including first through fourth conductive structures. The first conductive structure includes a first terminal and two first extending portions extending from the first terminal and configured as primary windings. The second conductive structure includes a second terminal and two second extending portions extending from the second terminal. A first via connects the third conductive structure to a first one of the two second extending portions, the third conductive structure and the first one of the two second extending portions thereby being configured as a first secondary winding. A second via connects the fourth conductive structure to a second one of the two second extending portions, the fourth conductive structure and the second one of the two second extending portions thereby being configured as a second secondary winding.

A variable reactance apparatus, tunable oscillator and method for changing a gain associated with an input signal of a tunable oscillator are disclosed. An embodiment of the variable reactance apparatus comprises includes a plurality of unit variable reactance structures comprising including respective control input nodes, and a control circuit configured to connect each of the control input nodes to a respective signal from among a plurality of signals comprising including a first tuning signal and a second tuning signal. An embodiment of a tunable oscillator comprises includes a resonance circuit, a negative impedance structure and a variable reactance apparatus configured for tuning of the oscillator. An embodiment of a method comprises includes altering connections of first and second tuning signals to control input nodes of respective first and second sets of unit variable reactance structures while holding constant a sum of the number of unit variable reactance structures in the first and second sets.

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.