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:
Jan. 16, 1990
Filed:
Apr. 11, 1988
Krishnaswamy Nagaraj, Scotch Plains, NJ (US);
AT&T Bell Laboratories, Murray Hill, NJ (US);
Abstract
A switched capacitor circuit with a very large time constant. Numerous low frequency analog applications, modems for example, require this type of circuit. The capacitances required to obtain a sufficiently large time constant are reduced over prior art techniques by as much as 50%. The circuit is insensitive to parasitic capacitances. The circuit comprises a switched input sampling capacitor, an operational amplifier and a first feedback capacitor connected in parallel with the amplifier. The switched sampling capacitor samples an input signal in a first clock phase. A second feedback capacitor is switched during the first phase to sample the output of the operational amplifier; and, in a second phase, it is switched in parallel with the first feedback capacitor of the amplifier.