Closed-loop audio attenuator
US4901350A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 20, 1989 |
| Grant date | Feb 13, 1990 |
| Priority date | — |
| Expiry date | Apr 20, 2009 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B1/1669
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A closed-loop attenuator for an FM stereo receiver provides attenuation to the L+R audio signal in a controlled and predictable reaction to an ultrasonic noise (USN) voltage presented to an input amplifier. This is accomplished through a closed-loop circuit configuration including a multiplier which modulates the current output of the input amplifier in accordance with the output of a master differential amplifier and supplies the modulated current to a gain stage connected to the input of the master differential amplifier. The output of the master amplifier is mirrored by a slave differential amplifier which applies the actual audio signal attenuation. The closed-loop configuration confines this linear control action to a very narrow range. Outside of this range, the circuit provides either full attenuation or no attenuation.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.