Common mode sensing and control in balanced amplifier chains
US4918399A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 9, 1988 |
| Grant date | Apr 17, 1990 |
| Priority date | — |
| Expiry date | Dec 9, 2008 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03F2203/45424
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
In a chain of fully differential amplifiers, having at least two cascaded amplifiers, the stabilization of the output common mode voltage of an amplifier is implemented by sensing the value of such a voltage by means of a dedicated terminal connected to a circuit node corresponding to the connected in common sources of the input differential pair of transistors of an amplifier which follows in the chain of cascaded amplifiers. Such a voltage is compared with a reference voltage to which, by means of a level shifting circuit, a voltage equivalent to the threshold voltage of the transistors forming the input pair is subtracted thus obtaining an error signal of the output common voltage of the amplifier to be stabilized which may be applied to a dedicated control terminal thereof. The system of the invention provides for the sensing of the output common mode voltage without loading the outputs of the amplifier to be stabilized and it is more easily implemented than known systems.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.