Analog volume control circuit
US4888810A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jan 19, 1989 |
| Grant date | Dec 19, 1989 |
| Priority date | — |
| Expiry date | Jan 19, 2009 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03G3/10
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A volume control circuit for hearing aids is adjustable to vary a control signal supplied to an amplifier between a microphone and receiver of a hearing air. The volume control circuit includes a positive voltage source, a charge holding circuit, and a switch for alternatively connecting the holding circuit with the positive voltage source to increase its voltage, with ground to decrease voltage, and with an open circuit to maintain a constant voltage. The holding circuit voltage is inverted around a predetermined reference voltage level, with the inverted signal amplified and applied to the gate terminal of an n-channel field effect transistor having its source terminal biased to a predetermined source voltage level, and its drain terminal electrically connected to the amplifier to provide the control signal. In response to charging of the holding circuit, the gate voltage is reduced to increase the FET impedance, thus decreasing the gain of the amplifier.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.