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US 8,866,557 B2Granted
XTAL oscillator
AssigneeBroadcom Corporation
InventorsChang-Hyeon Lee, Lindel Kabalican
Life of this patent
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Abstract
Resistor bias circuitry is included in components of an XTAL oscillator system to reduce 1/f noise. An XTAL oscillator includes a resistor bias circuit attached to the XTAL core. A common mode feedback OP amp connected to the XTAL core also includes a resistor bias circuit. An XTAL oscillator chain includes an XTAL core, common mode feedback OP amp, common mode logic buffer (CML BF), and differential to CMOS converter (D2C) each with resistor bias circuitry.
Claims20
A crystal oscillator comprising:
- a crystal oscillator core;
- a current generator;
- a transistor (M1) coupled to an output of the current generator and to a first resistor bias circuit further operatively coupled to the crystal oscillator core;
- a second resistor bias circuit coupled to the transistor (M1) and further coupled to the crystal oscillator core between ground and a common input to the crystal oscillator core, and
- wherein at least the second resistor bias circuit reduces noise of the crystal oscillator.
2 more elements
A crystal oscillator system comprising:
- a crystal oscillator core with first resistance bias circuitry;
- a common mode feedback OP amp operative with the crystal oscillator core, the common mode feedback OP amp further comprising second resistance bias circuitry;
- a common mode logic buffer coupled to the crystal oscillator core and further comprising third resistance bias circuitry;
- a differential to CMOS converter connected to the common mode logic buffer and further comprising fourth resistance bias circuitry, and
- wherein each of the resistance bias circuits reduces jitter of the crystal oscillator system.
2 more elements
A crystal oscillator comprising:
- a crystal oscillator core;
- a current generator;
- a transistor (M1) coupled to an output of the current generator;
- a resistor bias circuit coupled to the crystal oscillator core comprising:
- a first branch with a first resistor coupled between the transistor (M1) and a transistor (M2) of the crystal oscillator core,
- a second branch with a second resistor coupled between the transistor (M1) and a transistor (M3) of the crystal oscillator core, and
- a third branch with a bias resistor coupled between ground and a common input to the crystal oscillator core, and
- wherein the resistance bias circuit reduces 1/f noise of the crystal oscillator.
5 more elements
Dependencies are inferred from the claim text.