DC cancellation apparatus and method

Details DC cancellation apparatus and method DC cancellation apparatus and method

2005-04-05

2005-04-05

Wells, Kenneth B. (Department: 2816)

Miscellaneous active electrical nonlinear devices, circuits, and

Specific signal discriminating without subsequent control

By separating composite signal

C327S307000, C330S288000

Reexamination Certificate

active

06876233

ABSTRACT:
Methods and apparatus are provided for separating DC and AC components of a composite signal Is=Idc+Iac from a current source, e.g., a photodiode current source. Four current mirrors CM-1. . . CM-4are used with common branches and overlap. CM-1through CM-3mirror Is and CM-4mirrors Idc where lac has been removed by a frequency selective branch. Outputs of the Cm-3and Cm-4are combined at a node to provide a signal proportional substantially only to Iac. Complementary devices are used where Cm-1and Cm-4are of one type and Cm-2and Cm-3are of opposite type. The arrangement allows detection of AC signals (e.g., pulses) that are orders of magnitude smaller than the DC background. An I-to-V converter with a large feedback resistance is used at the output to produce a comparatively large voltage output proportional to lac.

REFERENCES:
patent: 5625281 (1997-04-01), Lambert
patent: 5703353 (1997-12-01), Blalock et al.
patent: 5900625 (1999-05-01), Baumgartner
patent: 20020089728 (2002-07-01), Kim

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