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:
Apr. 06, 1993
Filed:
Jul. 17, 1991
Applicant:
Inventor:
Nobutaka Amano, Tokyo, JP;
Assignee:
NEC Corporation, Tokyo, JP;
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
H03H / ;
U.S. Cl.
CPC ...
333 171 ; 307521 ;
Abstract
A cut-off frequency automatic adjusting filter includes a plurality of filters, one of them being a reference filter, and a feedback circuit for the reference filter. The feedback circuit is formed by a subtracter, a full-wave rectifier, an integrator and an error amplifier. A square wave signal is inputted to the reference filter as a reference signal instead of a sine wave signal in the conventional filter. The feedback circuit generates an electrical signal which causes the cut-off frequency of the reference filter and another filter to be constant.