Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Amplitude control
Reexamination Certificate
2005-01-18
2005-01-18
Wells, Kenneth B. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Amplitude control
C327S316000, C327S318000, C327S390000
Reexamination Certificate
active
06844768
ABSTRACT:
In a circuit having two input stages multiplexed to a common output stage having an output, one of the two input stages including transistor having a base, a collector and an emitter; a method of protecting the transistor from μ-degradation when the one of the two input stages is disabled comprises: clamping the base to a substantially fixed voltage for a first range of voltages applied to the one of the two input stages; and bootstrapping the base to a voltage that follows the output for a second range of voltages applied to the one of the two input stages. Alternatively, a method of protecting a transistor having a base connected through a finite impedance to an input voltage, a collector and an emitter, may comprise bootstrapping the base to a voltage that follows the input voltage with an offset when the input voltage is within a second range of voltages. A circuit having an input voltage connected thereto through a finite impedance may comprise: a transistor having a base, a collector and an emitter; a comparator having a comparator output and having an input connected between the base and the input voltage; a clamping circuit having an output connected to the base and an input connected through a series resistance to a clamping reference voltage; and a bootstrapping circuit responsive to the comparator output, the bootstrapping circuit having an output that injects a variable current into the series resistance, altering the behavior of the clamping circuit from a fixed voltage clamp to a follower.
REFERENCES:
patent: 4333120 (1982-06-01), Kotowski
patent: 4870533 (1989-09-01), Bahlmann
patent: 5235216 (1993-08-01), Cook et al.
patent: 5640127 (1997-06-01), Metz
patent: 5973561 (1999-10-01), Heaton
Bankman Jesse R.
Tam Kimo Y. F.
Analog Devices Inc.
Wells Kenneth B.
Wolf Greenfield & Sacks P.C.
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