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. 07, 1999
Filed:
Mar. 30, 1998
Hakan O Hemdal, Colorado Springs, CO (US);
Jeffrey M Brooke, Colorado Springs, CO (US);
Plasmon LMS, Inc., Colorado Springs, CO (US);
Abstract
A switchable active filter circuit is formed which employs a ground based switch to direct a portion of a feedback current away from a virtual ground terminal of an operational amplifier, thereby providing enhanced circuit Q and greater phase control at frequencies approaching an octave from the unity gain crossover frequency of an operational amplifier used to form the filter. The circuit employs a switchable feedback tee which includes a first capacitor, a second capacitor, a third capacitor and a switch. The first capacitor and the second capacitor form a first series circuit which is connected from the output terminal to the input terminal of the operational amplifier. The third capacitor and the first switch are connected as a second series circuit which is coupled from circuit ground potential to a junction of the first capacitor and the second capacitor. When the switch is closed, a feedback current flowing in the feedback tee is divided with a portion of the current flowing through the third capacitor to circuit ground, rather than into the virtual ground terminal of the operational amplifier. This filter topology is particularly well suited for use in a multi-mode read/write channel of a tape storage system.