Amplifier circuit of capacitor microphone
US8374363B2 · kind B2 · utility
Assignees
Inventor
Key dates
| Filing date | Mar 22, 2010 |
| Grant date | Feb 12, 2013 |
| Priority date | — |
| Expiry date | Mar 15, 2031 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04R3/00
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
In an amplifier circuit of a capacitor microphone, when a too high input signal from the capacitor microphone is inputted, the levels of output signals of the amplifier circuit are limited. A first feedback capacitor of an operational amplifier is formed using a changeable capacitance type MOS capacitor element, and has a characteristic of increasing the capacitance value CAf1 according to the amplitude of an input signal generated by a capacitor increases. Therefore, CAf (=CAf1+CAF2) increases according to the amplitude of the input signal increases, and accordingly the gain of the operational amplifier decreases, thereby limiting the output signals of the operational amplifier. This realizes the appropriate limitation of the output signals of the operational amplifier, even when the amplitude of the input signal becomes too high.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.