Oscillator circuit with automatic level control for selectively minimizing phase noise
AssigneeNational Semiconductor Corporation
InventorMark Alan Jones
Life of this patent
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Abstract
An oscillator with oscillator and voltage control circuitry for generating an oscillation signal having an amplitude that is automatically controlled for a selectively minimized phase noise. Automatic level control is used for controlling the amplitude of the oscillation signal such that the phase noise of the oscillation signal can be maintained at some selected level, e.g., minimized. The minimum signal voltage appearing across the oscillation circuit is monitored for controlling the bias of the circuit to prevent it from entering a saturation state, thereby avoiding adverse loading effects responsible for degraded phase noise performance.
Claims20
An apparatus including an oscillator with an oscillation signal amplitude that is automatically controlled for a selectively minimized oscillation signal phase noise, comprising:
- oscillator circuitry including first and second circuit terminals and an active circuit portion coupled between said first and second circuit terminals that, responsive to an amplitude control signal, generates an oscillator signal between said first and second circuit terminals, wherein said first and second circuit terminals are at first and second DC bias potentials, respectively, and said first DC bias potential is higher than said second DC bias potential;
- and
- voltage control circuitry, coupled to said oscillator circuitry, that, responsive to a comparison of a minimum signal voltage at said first circuit terminal and a maximum signal voltage at said second circuit terminal, generates said amplitude control signal such that a difference between said minimum and maximum signal voltages is maintained at a predetermined voltage amplitude.
An apparatus including an oscillator with an oscillation signal amplitude that is automatically controlled for a selectively minimized oscillation signal phase noise, comprising:
- oscillator circuitry including first and second circuit terminals and an active circuit portion coupled between said first and second circuit terminals that, responsive to an amplitude control signal, generates an oscillator signal between said first and second circuit terminals, wherein said first and second circuit terminals are at first and second DC bias potentials, respectively, and said first DC bias potential is higher than said second DC bias potential, and wherein said active circuit portion comprises a transistor which includes
- a first transistor terminal that is said first circuit terminal and conveys said minimum signal voltage, and
- a second transistor, terminal that is said second circuit terminal and conveys said maximum signal voltage;
- and
- voltage control circuitry, coupled to said oscillator circuitry, that, responsive to a comparison of a minimum signal voltage at said first circuit terminal and a maximum signal voltage at said second circuit terminal, generates said amplitude control signal such that a difference between said minimum and maximum signal voltages is maintained at a predetermined voltage amplitude, wherein said predetermined voltage amplitude comprises a saturation voltage for said transistor.
An apparatus including an oscillator with an oscillation signal amplitude that is automatically controlled for a selectively minimized oscillation signal phase noise, comprising:
- oscillator circuitry including first and second circuit terminals and an active circuit portion coupled between said first and second circuit terminals that, responsive to an amplitude control signal, generates an oscillator signal between said first and second circuit terminals, wherein said first and second circuit terminals are at first and second DC bias potentials, respectively, and said first DC bias potential is higher than said second DC bias potential;
- and
- voltage control circuitry, coupled to said oscillator circuitry, that, responsive to a comparison of a minimum signal voltage at said first circuit terminal and a maximum signal voltage at said second circuit terminal, generates said amplitude control signal such that a difference between said minimum and maximum signal voltages is maintained at a predetermined voltage amplitude, wherein said voltage control circuitry includes
- first voltage detection circuitry that detects said minimum signal voltage, and
- second voltage detection circuitry that detects said maximum signal voltage.
An apparatus including an oscillator with an oscillation signal amplitude that is automatically controlled for a selectively minimized oscillation signal phase noise, comprising:
- oscillator means including active circuit means for responding to an amplitude control signal by generating an oscillator signal across said active circuit means;
- and
- voltage controller means for responding to a comparison of a minimum signal voltage at a first node of said active circuit means and a maximum signal voltage at a second node of said active circuit means by generating said a amplitude control signal such that a difference between said minimum and maximum signal voltages is maintained at a predetermined voltage amplitude, wherein said first and second nodes are at first and second DC bias potentials, respectively, and said first DC bias potential is higher than said second DC bias potential.
An apparatus including an oscillator with an oscillation signal amplitude that is automatically controlled for a selectively minimized oscillation signal phase noise, comprising:
- oscillator means including active circuit means for responding to an amplitude control signal by generating an oscillator signal across said active circuit means;
- and
- voltage controller means for responding to a comparison of a minimum signal voltage at a first node of said active circuit means and a maximum signal voltage at a second node of said active circuit means by generating said amplitude control signal such that a difference between said minimum and maximum signal voltages is maintained at a predetermined voltage amplitude, wherein said first and second nodes are at first and second DC bias potentials, respectively, and said first DC bias potential is higher than said second DC bias potential, wherein said voltage controller means includes
- first voltage detector means for detecting said minimum signal voltage, and
- second voltage detector means for detecting said maximum signal voltage.
A method for generating an oscillation signal amplitude that is automatically controlled for a selectively minimized oscillation signal phase noise, comprising the steps of:
- operating an active circuit between first and second circuit terminals, wherein said first and second circuit terminals are at first and second DC bias potentials, respectively, and said first DC bias potential is higher than said. second DC bias potential;
- receiving an amplitude control signal;
- generating, in response to said amplitude control signal, an oscillator signal with a minimum signal voltage at said first circuit terminal and a maximum signal voltage at said second circuit terminal, wherein a difference between said minimum and maximum signal voltages is maintained at a predetermined voltage amplitude;
- comparing said minimum and maximum signal voltages;
- and
- generating said amplitude control signal in response to said voltage comparison.
A method for generating an oscillation signal amplitude that is automatically controlled for a selectively minimized oscillation signal phase noise, comprising the steps of:
- operating an active circuit between first and second circuit terminals, wherein said first and second circuit terminals are at first and second DC bias potentials, respectively, and said first DC bias potential is higher than said second DC bias potential;
- receiving an amplitude control signal;
- generating, in response to said amplitude control signal, an oscillator signal with a minimum signal voltage at said first circuit terminal and a maximum signal voltage at said second circuit terminal, wherein a difference between said minimum and maximum signal voltages is maintained at a predetermined voltage amplitude;
- comparing said minimum and maximum signal voltages by detecting said minimum signal voltage and detecting said maximum signal voltage;
- and
- generating said amplitude control signal in response to said voltage comparison.
Dependencies are inferred from the claim text.