Apparatus and method for an input stage of an operational amplifier
US5142243A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 19, 1990 |
| Grant date | Aug 25, 1992 |
| Priority date | — |
| Expiry date | Dec 19, 2010 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03F2203/45674
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
An operational amplifier input stage includes two transistors coupled as a differential amplifier to receive input signals. At least one transistor is stacked in a load circuit of each input transistor for the purpose of lowering the voltage across each transistor. In order to eliminate the effects of error currents resulting from conventional resistor self biasing of the stacked transistors, two nodes, to which the input transistors are coupled, are identified. A feedback circuit is coupled to each node and each feedback circuit maintains the coupled node at a voltage level established by the feedback apparatus of the operational amplifier. The disclosed circuit eliminates circuit drift and offset voltages resulting from changes in common mode and/or power supply voltages by eliminating the effects of resistive loading on the input stage components.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.