High speed fully differential operational amplifier with fast settling time for switched capacitor applications
US5847607A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 19, 1996 |
| Grant date | Dec 8, 1998 |
| Priority date | — |
| Expiry date | Dec 19, 2016 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03F2203/45651
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A high speed fully differential operational amplifier with fast settling time for switched capacitor applications includes a high gain active cascode applied to the operational amplifier's input stage transistors to improve the gain, provide a higher output impedance, and thus, reduce the Miller feedback gate drain capacitance of the input stage devices. This improves the speed of the amplifier. A biasing technique is used to keep the active cascodes biased during transient overload so that settling will not be adversely affected during the recovery of the cascodes. A pair of transistors are used to feed forward a fraction of the tail current to "keep-alive" the cascode transistors. In other words, the fraction of the tail current that is fed to the source of the cascode transistors via the keep-alive transistors effectively biases the active cascodes sufficiently so that they do not turn off completely during slewing.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.