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:
Jun. 18, 2002
Filed:
Feb. 07, 2001
Brian C. Martin, Carlsbad, CA (US);
National Semiconductor Corporation, Santa Clara, CA (US);
Abstract
A Sallen-Key filter circuit having an operational amplifier of unity gain is tuned by replacing a resistor of the circuit with an adjustable resistor ladder network. The ladder network has an input and first and second output terminals and a plurality of arms connected in series between the input and first output terminal. Each arm has a resistor R and a node separating each pair of adjacent arms, a shunt arm connected to each node, each shunt arm having a resistor which has a value which is a multiple of R and a switch in series. Each switch controls connection of the respective shunt arm to the first or second output terminal, such that the resistance of the ladder network is varied dependent on the switch positions. The first output terminal is connected to the amplifier output and the second output terminal is connected to the amplifier positive input.