Rail-to-rail output stage of an operational amplifier
US5140280A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 30, 1991 |
| Grant date | Aug 18, 1992 |
| Priority date | — |
| Expiry date | Aug 30, 2011 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03F2203/45732
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
An input stage of an operational amplifier uses current sources to allow first and second differential input transistor pairs to operate near the power supply rails. The output stage of the operational amplifier also operates within a saturation potential of the power supply rails. The first differential input transistor pair operates when the input signal is less than a predetermined threshold, while the second differential input transistor pair operates when the input signal is greater than the predetermined threshold. A detection circuit at the input terminals prevents phase inversion of the output signal should the inputs be driven beyond the power supply rails. A current cancellation circuit removes current variation induced by voltage changes at the output of the input stage and provides high gain and low input offset voltage.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.