Microphone filter and microphone unit
US6516069B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Jul 5, 2000 |
| Grant date | Feb 4, 2003 |
| Priority date | — |
| Expiry date | Mar 9, 2021 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04R3/00
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A large-time-constant microphone filter which contains resistance and capacitance as its constituent and can be formed in the same semiconductor chip as a microphone unit is achieved, which results in downsizing and cost reduction of the microphone unit. A transistor of a current mirror circuit is used as a resistance of a microphone filter, utilizing a differential resistance produced by a channel length modulation effect of the transistor or an Early effect. When variations in the drain-source voltage of the transistor occur, the drain-source current of the transistor slightly varies in linear characteristics and the transistor serves a high value of resistance. Being a current mirror circuit, the microphone filter is resistant to characteristic variations due to temperature changes and can be formed in a semiconductor chip without a significant increase in chip area.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.