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:
Aug. 11, 1998
Filed:
Jan. 06, 1997
Fujitsu Limited, Kanagawa, JP;
Abstract
A voltage-controlled oscillator has first and second switched capacitor filters, an operational amplifier, and a comparator. The first switched capacitor filter is controlled by a control clock signal to supply a positive current depending on an input voltage, and the second switched capacitor filter is controlled by the control clock signal to supply a negative current depending on the input voltage. The operational amplifier has an input terminal alternately connectable to the first and second switched capacitor filters by a first switch which can be rendered conductive in synchronism with an output clock signal, and another input terminal for being supplied with a constant voltage. A potential at an output terminal of the operational amplifier is lowered when the operational amplifier is supplied with the positive current through a feedback circuit which is provided between the input terminal and the output terminal, and is increased when the operational amplifier is supplied with the negative current through the feedback circuit. The comparator compares the potential at the output terminal of the operational amplifier alternately with a first constant voltage and a second constant voltage, lower than the first constant voltage, which can be switched in synchronism with the output clock signal, thereby to produce the output clock signal.