Linear, Voltage-Controlled Ring Oscillator With Current-Mode, Digital Frequency And Gain Control
First Claim
1. A voltage-controlled ring oscillator, comprising:
- a bias current generator, the bias current generator comprising one or more controllable current sources, at least one of the controllable current sources generating a portion of the bias current in response to an analog tuning voltage, and at least one other of the controllable current sources generating another portion of the bias current in response to a digitally controlled network of linearly responsive current source transistors; and
a plurality of inverters coupled in a ring with each other and defining an oscillator circuit, each inverter receiving the bias current.
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Abstract
In a voltage-controlled ring oscillator, one or more controllable current sources generate a bias current in response to a tuning voltage. Any of several features can be included to promote frequency tuning linearity. In accordance with one feature, the ring oscillator circuit transistors can be sized relative to one another to skew the rise and fall times of the ring oscillator output signal with respect to one another. In accordance with another feature, a peak limiter can limit the oscillation amplitude in response to the bias current. In accordance with still another feature, a controllable bias current source can include a voltage-to-current converter and one or more groups of digitally controlled current source transistors.
31 Citations
19 Claims
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1. A voltage-controlled ring oscillator, comprising:
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a bias current generator, the bias current generator comprising one or more controllable current sources, at least one of the controllable current sources generating a portion of the bias current in response to an analog tuning voltage, and at least one other of the controllable current sources generating another portion of the bias current in response to a digitally controlled network of linearly responsive current source transistors; and a plurality of inverters coupled in a ring with each other and defining an oscillator circuit, each inverter receiving the bias current. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method for operating a voltage-controlled ring oscillator, comprising:
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generating a bias current by controlling one or more controllable current sources, at least one of the controllable current sources generating a portion of the bias current in response to an analog tuning voltage, and at least one other of the controllable current sources generating another portion of the bias current in response to a digitally controlled network of linearly responsive current source transistors; and biasing a plurality of inverters with the bias current, the inverters coupled in a ring with each other to define an oscillator circuit. - View Dependent Claims (14, 15, 16, 17, 18, 19)
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Specification