Expander circuit with reduced distortion

Details Expander circuit with reduced distortion Expander circuit with reduced distortion

2011-06-14

2011-06-14

Chin, Vivian (Department: 2614)

Electrical audio signal processing systems and devices

Including amplitude or volume control

With amplitude compression/expansion

C381S120000, C381S028000, C381S107000, C333S014000, C333S032000, C333S124000, C330S282000, C455S072000

Reexamination Certificate

active

07961896

ABSTRACT:
Systems for an expander circuit are disclosed. An expander circuit comprising a transmit amplifier for amplifying electrical signals received from a microphone. A rectifier circuit is responsive to the electrical signals and generates a D.C. voltage. A dynamic resistor circuit is coupled to the transmit amplifier for regulating the gain of the transmit amplifier. The dynamic resistor circuit includes a bipolar junction transistor for receiving the D.C. voltage. The bipolar junction transistor is operated such that the collector current is zero and the bipolar junction transistor has a variable impedance seen by the transmit amplifier dependent upon the D.C. voltage.

REFERENCES:
patent: 3903485 (1975-09-01), Dolby
patent: 4012688 (1977-03-01), Blackburn et al.
patent: 4241453 (1980-12-01), Drake
patent: 4710725 (1987-12-01), White et al.
patent: 5337368 (1994-08-01), Kikuchi et al.
patent: 6549630 (2003-04-01), Bobisuthi
patent: 7423487 (2008-09-01), Fornasari et al.

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