Oscillators – Ring oscillators
Patent
1997-08-25
1998-10-13
Mis, David
Oscillators
Ring oscillators
331 34, 331175, 331177R, 331185, 327 52, 327100, 330295, H03B 524, H03B 504, H03L 100, H03F 345
Patent
active
058218246
ABSTRACT:
A multistage voltage-to-current ("VI") converter for producing, in response to an input voltage, an output voltage useful for controlling a voltage-controlled oscillator ("VCO"). Preferably, the transfer function of the VI converter is such that the output clock frequency-to-input voltage transfer function (of a system including the VI converter and the VCO) is at least approximately linear over a desired output clock frequency range and has a desired slope in such range. In preferred embodiments, the multistage VI converter includes three differential amplifier stages connected in parallel. Each stage has a tail current and receives a reference voltage (the tail currents and reference voltages typically differ from stage to stage), and produces a component of a total current. The total current determines the output voltage. Optionally, bias circuitry is provided for producing nonzero output voltage in response to zero input voltage. In other embodiments, the multistage VI converter includes two stages or more than three stages connected in parallel, each stage producing a component of a total current which determines the output voltage. The number of stages, and the tail current and reference voltage (and resistor values and transistor characteristics) of each stage, are chosen to achieve a desired output voltage-to-input voltage transfer function. Another aspect of the invention is a VCO system including any embodiment of the multistage VI converter of the invention.
REFERENCES:
patent: 5079515 (1992-01-01), Tanimoto
Mis David
National Semiconductor Corporation
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