Common mode feedback for large output swing and low differential error
US7592867B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Apr 3, 2007 |
| Grant date | Sep 22, 2009 |
| Priority date | — |
| Expiry date | Jul 13, 2027 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03F2203/45681
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A differential amplifier includes a differential input pair (2A) coupled to a folded cascode stage (2B) and a common mode feedback circuit (34) including a tracking circuit (30A) coupled to first (Vout−) and second (Vout+) outputs of the folded cascode stage (2B). The first and second outputs are coupled to first terminals of first (31A) and second (31B) tracking capacitors which have second terminals on which a first common mode output signal (VCM1) is produced and also are coupled to first terminals of third (32A) and fourth (32B) tracking capacitors, respectively, which have second terminals on which a second common mode output signal (VCM2) is produced. The first and third tracking capacitors are discharged by first (27A) and second (27B) switches that directly couple the first and second outputs to first and second inputs of a common mode feedback amplifier (4). A desired common mode output voltage (VCM-IN) is applied to a third input of the common mode feedback amplifier. The switches are opened to cause the first and second common mode output voltages to be generated, causing a common mode feedback control signal (VCMFB) to be generated for biasing the folded cascode stage.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.