Double sampled biquad switched capacitor filter
US5495200A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 6, 1993 |
| Grant date | Feb 27, 1996 |
| Priority date | — |
| Expiry date | Apr 6, 2013 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03H19/004
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A biquad switched capacitor filter is preferably utilized as the output filter in a sigma delta digital-to-analog converter. The switched capacitor filter uses a cross-coupled switched capacitor circuit which delivers charge to the capacitors on both phases of the clock. As a result, the sizes of the capacitors can be reduced by a factor of two, while delivering the same charge as a single sampling circuit. By using the cross-coupled switching circuit everywhere in the filter, the sensitivity to capacitor mismatches is substantially reduced. The clock phases applied to the stages of the filter are alternated so that there is a one clock cycle delay around each loop containing two filter stages, thereby insuring the stability of the filter.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.