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:
Dec. 11, 2001
Filed:
Aug. 12, 1999
Navid Foroudi, Ottawa, CA;
Nortel Networks Limited, Montreal, CA;
Abstract
A charge pump circuit for a phase locked loop includes series-connected FETs in which a reference current flows and other series-connected FETs in which sourcing and sinking currents flow. The junctions of the two series-connected FETs are connected to the non-inverting and inverting input terminals of an operational amplifier. The amplifier detects the voltage difference between a reference side junction and the output voltage of the charge pump circuit and provides an amplified voltage of the detected voltage difference. In response to the amplified voltage, the charge pump circuit sources to and sinks current from an external circuit to which the charge pump circuit is connected. Due to the definite and high input impedance of the operational amplifier, there is no mismatch between the source and the sink currents. A start-up FET initializes the charge pump circuit so that current flows in the series-connected FETs.