Current repeater
US4473794A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 21, 1982 |
| Grant date | Sep 25, 1984 |
| Priority date | — |
| Expiry date | Apr 21, 2002 |
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) symetrically 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. A current repeater circuit (FIG. 8) is employed generally throughout the integrated circuit amplifier for driving various elements. The current repeater comprises at least one unipolar transistor to permit operation at low direct current voltages, while providing an accurately controlled curr…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.