Oscillators – Ring oscillators
Patent
1993-02-03
1994-07-19
Dolinar, Andrew M.
Oscillators
Ring oscillators
331 17, H03K 3354
Patent
active
053312953
ABSTRACT:
A voltage controlled oscillator (VCO) provides an output signal with an output frequency that varies only minimally for any given input control voltage despite variations in the manufacturing process, temperature and supply voltage. The VCO also includes a multistage ring oscillator which includes a plurality of series-connected current-starved inverter stages. The VCO utilizes a first current source to provide a substantially constant current independent of process, temperature and supply voltage and a second current source to provide a variable current that varies in response to process, temperature and supply voltage. Both current sources generate a respective current signal independent of the input signal to the VCO. An attenuator, responsive to the VCO's input voltage signal (typically from a phase-locked loop filter) provides a control current signal to the ring oscillator. The attenuator receives a supply current created by subtracting the second current from the first current, and utilizes a differentiation subcircuit that attenuates the supply current in response to changes in an input voltage to produce a current control signal that sets the current level in the ring oscillator's cells. The frequency of oscillation of the ring oscillator is determined by the control current signal. Additionally, the VCO circuit may include a current mirror for receiving the control current signal from the attenuator and mirroring the control current signal to the ring oscillator.
REFERENCES:
patent: 4015219 (1977-03-01), Kawagoe et al.
patent: 4072910 (1978-02-01), Dingwall et al.
patent: 4714900 (1987-12-01), Sata
patent: 4987373 (1991-01-01), Soo
patent: 5061907 (1991-10-01), Rasmussen
patent: 5136260 (1992-08-01), Yocousefi-Elezei
Deng Jay
Jelinek Jules J.
Dolinar Andrew M.
National Semiconductor Corporation
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