Electrical audio signal processing systems and devices – With amplifier
Reexamination Certificate
2006-05-09
2006-05-09
Mei, Xu (Department: 2644)
Electrical audio signal processing systems and devices
With amplifier
C381S094500, C330S051000, C330S295000, C330S296000, C330S297000, C330S298000
Reexamination Certificate
active
07043033
ABSTRACT:
An audio amplifier system includes two amplifiers that are configured to drive loads through either DC or AC coupling. A third amplifier provides an AC ground return when the system is configured in the DC coupled mode, and is disabled when the system is configured in the AC coupled mode. A bypass circuit charges a bypass capacitor to provide a reference voltage level for the amplifiers. A mode detection circuit monitors the reference voltage level and the output of the third amplifier to determine the current operating mode. The third amplifier is disabled when the reference voltage exceeds the output of the third amplifier or when a shutdown condition is activated, such that the third amplifier is protected from short circuit conditions. The charge and discharge times of the bypass capacitor relate to the detected operating mode minimize click and pop in the amplified signals.
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“LM4911 Boomer Stereo 40mW headphone Amplifier with Selectable Capacitive Coupled or OCL Output,” National Semiconductor, Jul. 2001, pp. 1-5.
“LM4901 Boomer 1 Watt Audio Power Amplifier with Selectable Shutdown Logic Level,” National Semiconductor, Dec. 2001, pp. 1-21.
“LM4910 Boomer Output Capacitor-less Stereo 35mW Headphone Amplifier,” National Semiconductor, Jan. 2002, pp. 1-19.
Hertzberg Brett A.
Mei Xu
Merchant & Gould P.C.
National Semiconductor Corporation
Suthers Douglas
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