Electrical audio signal processing systems and devices – Circuitry combined with specific type microphone or loudspeaker – With electrostatic microphone
Reexamination Certificate
2006-08-15
2006-08-15
Lee, Ping (Department: 2644)
Electrical audio signal processing systems and devices
Circuitry combined with specific type microphone or loudspeaker
With electrostatic microphone
C381S317000, C330S009000, C327S124000
Reexamination Certificate
active
07092538
ABSTRACT:
A method and apparatus for substantially reducing and virtually eliminating direct current flow through the input transistor(s) of an input buffer circuit for an electret microphone is disclosed. An input transistor is provided and operably connected to an input and an output of the input buffer circuit. The input transistor has a first operating state wherein current flow occurs in a first direction and a second operating state wherein the a current flow occurs in a second direction—opposite that of the first direction. The input transistor is biased to alternately control operation between the first operating state and the second operating state. The alternating, opposing flows of current of the respective operating states cooperate to substantially reduce and virtually eliminate the flow of direct current through the input transistor(s) of the buffer circuit. A reduction in excess noise associated with the input transistor results from the substantially decreased direct current flow through the input transistor(s) of the buffer circuit.
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European Search Report for Application No. 03 25 2381 dated Mar. 15, 2004.
Boor Steven E.
Potter Robert C.
Knowles Electronics LLC
Lee Ping
Marshall & Gerstein & Borun LLP
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