Microphone bias current measurement circuit

Details Microphone bias current measurement circuit Microphone bias current measurement circuit

1998-12-18

2003-08-19

Isen, Forester W. (Department: 2644)

Electrical audio signal processing systems and devices

Circuitry combined with specific type microphone or loudspeaker

C381S120000, C330S262000

Reexamination Certificate

active

06608905

ABSTRACT:

FIELD OF THE INVENTION
This invention generally relates to electronic systems and in particular it relates to microphone bias current measurement circuits.
BACKGROUND OF THE INVENTION
The current microphone of choice in the telecom industry is an electret microphone. This particular type of low cost microphone needs a bias current flowing through it to maintain proper operation.
SUMMARY OF THE INVENTION
Generally, and in one form of the invention, the microphone bias current detection circuit includes: a microphone circuit; an amplifier having a first output and a second output, the first output is coupled to the microphone circuit for providing a bias current to the microphone circuit, the second output provides a sampled current proportional to the bias current; a first switch having a first end coupled to the second output of the amplifier; a resistor having a first end coupled to a second end of the first switch; and a second switch coupled between the first end of the resistor and a reference current source.


REFERENCES:
patent: 5627494 (1997-05-01), Somerville
patent: 5832076 (1998-11-01), Holthaus et al.
patent: 5838804 (1998-11-01), Holthaus et al.

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