Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – Unwanted signal suppression
Reexamination Certificate
2008-03-04
2008-03-04
Le, Dinh T. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
Unwanted signal suppression
C327S554000
Reexamination Certificate
active
07339418
ABSTRACT:
In one embodiment, a differential filter is configured using a differential operational amplifier (op-amp) with two feedback RC networks, each RC network coupled between a respective input and a respective output of the op-amp. Two capacitive elements may each provide mid-band positive feedback from a respective output of the op-amp to the midpoint of a respective corresponding resistive element, where each resistive element is coupled to a respective input of the op-amp. The mid-band positive feedback may operate to convert a first-order response of the filter to a second-order response. In one set of embodiments, dielectric absorption (DA) cancellation may be implemented with positive RC feedback from a divided version of a respective one of the op-amp outputs. For cascaded filters, DA cancellation may be implemented with positive RC feed-forward. Transistors coupled across the feedback RC networks may be used to disable the filter, decoupling the filter from other circuit components when the filter is not in use.
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Hood Jeffrey C.
Le Dinh T.
Meyertons Hood Kivlin Kowert & Goetzel P.C.
National Instruments Corporation
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