Low voltage high frequency ring oscillator for controling phase-shifted outputs
AssigneeSGS-Thomson Microelectronics S.A.
InventorsTrevor K. Monk, Andrew M. Hall
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Abstract
A oscillator having two synchronized oscillator rings is described. Synchronization is accomplished by circuitry connected between the outputs of two aligned stages in coupled oscillator rings, the circuitry being operable to maintain outputs of the stages 180.degree. apart in phase.
Claims20
An oscillator comprising:
- two oscillator rings, each oscillator ring comprising the same number of oscillator stages, each stage having a single input and a single output and being operable to provide at said output an output signal which is phase-shifted by a controllable amount relative to an input signal provided at said input, each stage having a current source arranged to receive a control signal to adjust said phase-shift, the input of each stage being connected to receive the output of a preceding stage, wherein the oscillator further comprises synchronization circuitry connected between the outputs of two aligned stages in the coupled oscillator rings and operable to maintain said outputs 180.degree. apart in phase.
A circuit having two aligned stages of respective rings to provide a differential oscillator stage for a ring oscillator, said circuit comprising:
- a first pair of transistors, one transistor of said first pair of transistors being gated by an input signal and the other being gated to a first output node, and said first pair of transistors being connected between said first output node and a first reference voltage;
- a second pair of transistors each connected between a second output node and a second reference voltage having one gate of said second pair of transistors connected to said first output node and the other connected to said second output node;
- a third pair of transistors each being connected between a third output node and a third reference voltage and having one gate of said third pair of transistors connected to said second output node and the other connected to said third output node and providing said input signal;
- and
- respective current sources connected to said output nodes and controllable to control the speed of each stage, the gain of each stage being set by the ratio of size of the first pair of transistors to the second pair of transistor, wherein the ratio of sizes between the third pair of transistors and the second pair of transistors is selected so that the transistors operate in a saturation region to provide a linear differential inverting stage.
An oscillator comprising two oscillator rings, each oscillator ring including the same number of oscillator stages, each stage having a single input and a single output and comprising a first n-channel field-effect transistor having a source/drain path connected between an output node and a reference voltage and a gate acting as an input node to the stage, the input of each stage being connected to receive the output of a preceding stage, wherein the oscillator further comprises synchronization circuitry connected between the outputs of two aligned stages in the two oscillator rings and operable to maintain said outputs 180.degree. apart in phase, each stage further comprising:
- a second n-channel field effect transistor having a source/drain path connected between the output node and the reference voltage and having a gate connected to the output node;
- and
- a controllable current source connected to the output node and comprising a p-channel MOS field-effect transistor arranged to be gated by a control voltage to adjust said phase shift, wherein each stage is operable to provide at said output an output signal which is phase-shifted by a controllable amount relative to an input signal provided at said input.
Dependencies are inferred from the claim text.