DC cancellation apparatus and method
US6876233B1 · kind B1 · utility
Assignee
Inventor
Key dates
| Filing date | Feb 15, 2003 |
| Grant date | Apr 5, 2005 |
| Priority date | — |
| Expiry date | Feb 15, 2023 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03K5/003
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
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-4 are used with common branches and overlap. CM-1 through CM-3 mirror Is and CM-4 mirrors Idc where lac has been removed by a frequency selective branch. Outputs of the Cm-3 and Cm-4 are combined at a node to provide a signal proportional substantially only to Iac. Complementary devices are used where Cm-1 and Cm-4 are of one type and Cm-2 and Cm-3 are 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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.