High input impedance circuit
US4629910A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 21, 1985 |
| Grant date | Dec 16, 1986 |
| Priority date | — |
| Expiry date | Oct 21, 2005 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03F3/1855
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
An integrated circuit amplifier for a high impedance microphone (100) of the capacitance type is disclosed. The subject amplifier circuit permits the further miniaturization of an electret microphone as it is capable of providing an input impedance simulating a resistor value of hundreds of megohms. The circuit particularly comprises duplicate coupling circuits (101a and 101b), a source of reference direct current voltage (103), and a gain providing circuit (102). The coupling circuits (101a and 101b) comprise a first pair of diodes (Q1 and Q2) symmetrically placed about one input terminal (IN1) of the microphone (100). Outputs of the reference voltage source (103) are provided to coupling circuits (101a and 101b) and through the coupling circuits to gain providing circuit 102. Such an arrangement facilitates power supply noise rejection and automatic canceling of direct current voltage drifts.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.