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:
Sep. 17, 2002
Filed:
Feb. 13, 2001
Iuri Mehr, North Andover, MA (US);
Analog Devices, Inc., Norwood, MA (US);
Abstract
A tunable, active RC filter and method of tuning the active RC filter which prevents distortions introduced during tuning. Generally, each tuning element in the feedback loop of the tunable active RC filter comprises a capacitor, a first switch, a second switch, and a third switch. The first switch connects a first terminal of the capacitor to a summing junction at the input of the op-amp when closed. When closed, a second switch connects the first terminal of the capacitor to a replica of the voltage present at the summing junction (input) of the op-amp to which the first terminal of the reactance element is connectable via the first switch. A third switch, when closed, connects the first terminal of the capacitor to the second terminal of the reactance element, which is connected the output of the op-amp. By connected the capacitor to the replica voltage via the second switch prior to connecting it to the summing junction at the input of the op-amp, the capacitor is pre-charged to the voltage it would have if present in the feedback path. Therefore, as the capacitor is pre-charged, the output voltage of the op-amp is not presented to the summing junction when the capacitor is switched in, which substantially eliminates the distortions caused by connecting the capacitors to the summing junction. The third switch is utilized to short the capacitor when it is disconnected from the summing junction.