The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 08, 1996
Filed:
Aug. 15, 1995
Harry S Jackson, Austin, TX (US);
SigmaTel Inc., Austin, TX (US);
Dallas Semiconductor Corp., Dallas, TX (US);
Abstract
A method and apparatus for a controlled oscillator which may be incorporated in a phase locked loop is accomplished by including a current controlled reference, a current mirror and a plurality of inverters that form a ring oscillator within the controlled oscillator. The controlled reference provides a current control signal to the current mirror, which, in turn, provides a load control signal to each inverter of the ring oscillator. Each inverter is characterized by a differential load section which includes a pair of load transistors for receiving the load control signal and for providing a current source from the load control signal and a pair of clamping transistors configured to provide a non-linear clamping circuit which limits the voltage range of a differential output. The load transistors are connected in parallel with the clamping transistors to provide a linear differential output. The load control signal dynamically regulates the impedance of the differential load section such that the controlled oscillator may stablely operate at any frequency and be produced without performance variations due to variances in the fabrication process.