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:
Mar. 18, 2003
Filed:
Jul. 19, 2000
Sergio Pernici, Bergamo, IT;
Germano Nicollini, Piacenza, IT;
STMicroelectronics S.r.l., Agrate Brianza, IT;
Abstract
A receiver portion of a telephone includes a differential amplifier stage with a single output, an electroacoustic transducer connected between the output, via a capacitor and ground and a unit for controlling switching on/off, connected to the differential stage for the activation or deactivation thereof. To prevent annoying noises in the transducer upon switching on and off, the differential stage includes an operational amplifier having a first capacitor and a second capacitor in series with the inverting and the non-inverting input terminals. A third capacitor is connected between the inverting input and the output of the operational amplifier. A fourth capacitor is connected between the non-inverting input and a first reference-voltage terminal. A first switching capacitor is alternatively connectable between a second and a third reference-voltage terminal, or between the first input and the output of the operational amplifier. A second switching capacitor is alternatively connectable between a fourth and a fifth reference-voltage terminal, or between the second input of the operational amplifier and the fifth reference-voltage terminal.