Noise reduction circuit
US4441083A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 8, 1981 |
| Grant date | Apr 3, 1984 |
| Priority date | — |
| Expiry date | Sep 8, 2001 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03G9/025
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A noise reduction circuit for use in an audio signal recording/reproducing apparatus is comprised of a first signal path including a voltage-controlled amplifier for amplifying a signal supplied thereto with controllable gain and a differentiating circuit for differentiating at least that portion of the signal passing through the voltage-controlled amplifier within the audio range; a level detecting circuit for controlling the gain of the voltage-controlled amplifier in response to the level of the signal passing through the voltage-controlled amplifier; a feedback resistor connected as a negative feedback path with the first signal path for providing an upper limit to the gain imparted to the signal supplied to the noise reduction circuit; a subtraction circuit for subtracting the negatively fed back signals from the signal supplied to the noise reduction circuit to produce an input signal for the first signal path; a second resistor or a low-pass filter connected as a positive feedforward path between the input of the noise reduction circuit and the output of the first signal path for providing a lower limit to the gain imparted to the signal supplied to the noise reduction circu…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.