Electret condensor microphone preamplifier that is insensitive to leakage currents at the input
US7110560B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Mar 8, 2002 |
| Grant date | Sep 19, 2006 |
| Priority date | — |
| Expiry date | Sep 18, 2023 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03G11/02
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A preamplifier having extremely high input impedance amplifies the electrical signal output from an electret condenser microphone (ECM) without suffering from the effects of a DC leakage current at the input. The preamplifier circuit includes a pair of cross-coupled PN junction diodes setting the input impedance, a PMOS device, and a load resistor configured similarly to a conventional preamplifier. A capacitor is placed between the input and the cross-coupled diodes such that a DC path no longer exists to bias the cross-coupled diodes. Therefore, leakage currents are prevented from upsetting the DC operating point of the preamplifier and biasing the cross-coupled diodes. Consequently, small signal gain distortion, excessive demodulation products and increased noise can be avoided.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.