Amplifiers – With semiconductor amplifying device – Including differential amplifier
Reexamination Certificate
2007-12-21
2009-06-02
Nguyen, Patricia (Department: 2817)
Amplifiers
With semiconductor amplifying device
Including differential amplifier
C330S257000, C330S297000, C330S296000
Reexamination Certificate
active
07541872
ABSTRACT:
A multi-stage circuit has a first stage powered by the output voltage of a next stage. A current source within the first stage provides a tail current for a differential amplifier within the first stage. When the first stage has an operating voltage high enough for proper operation, this tail current is at a nominal level; if the voltage is too low for proper operation of the first stage, the tail current is below this nominal level. A comparator, which has one input coupled to a node within this current source, a second input coupled to a threshold voltage, and an output coupled to a control node within the next stage, provides an output indicative of whether or not the tail current is substantially at its nominal level. If tail current is too low, the comparator provides a forcing signal to the control node of the next stage which causes the output of the next stage to be at a substantially nominal level regardless of the voltage at its input, thus providing a suitably high voltage for the first stage to begin normal operation. When the tail current reaches its nominal level, the comparator output changes state to one which has little or no effect on the output voltage of the second stage, and normal operation of the overall circuit begins.
REFERENCES:
patent: 4160201 (1979-07-01), Ahmed
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patent: 7061337 (2006-06-01), Partovi et al.
patent: 7463068 (2008-12-01), Lee et al.
patent: 2008/0089533 (2008-04-01), Theus et al.
Brady III Wade J.
Nguyen Patricia
Patti John J.
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
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