Receiver portion of a telephone
US6535724B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Jul 19, 2000 |
| Grant date | Mar 18, 2003 |
| Priority date | — |
| Expiry date | Jun 9, 2021 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03G3/348
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.