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:
Jul. 14, 1992
Filed:
Nov. 03, 1989
Mead C Killion, Elk Grove Village, IL (US);
Norman P Matzen, Campbell, CA (US);
Clyde M Brown, Jr, Cupertino, CA (US);
William A Cole, Mossby, CA;
James B Compton, Los Gatos, CA (US);
Steven J Iseberg, Schaumburg, IL (US);
Jonathan K Stewart, Bensenville, IL (US);
Donald L Wilson, Roselle, IL (US);
Etymotic Research Inc., Elk Grove Village, IL (US);
Abstract
A high fidelity hearing aid amplifier is operable at a very low battery voltage and includes a single integrated circuit chip which provides a variable gain amplifier and gain control circuitry operative at low signal levels to enhance gain at higher frequencies relative to gain at lower frequencies, such circuitry including a logarithmic rectifier arrangement and a peak detector in a compression ratio control circuit. Operation at a low battery voltage is enhanced through a compression ratio control circuit which provides a level shift between an AC output of the logarithmic rectifier arrangement and the peak detector. Current mirrors are provided to obtained balanced and stable operation, and an arrangement is provided for manual control by a user to obtain an optimum response characteristic.