Selectable trimming circuit for use with a digital to analog converter
US4138671A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 14, 1977 |
| Grant date | Feb 6, 1979 |
| Priority date | — |
| Expiry date | Feb 14, 1997 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03M1/447
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
The outputs of individual stages in a digital to analog converter are each trimmed by independent circuitry which includes a plurality of transistors connected to a common output terminal, the physical dimensions of each transistor being scaled in proportion to desired levels of current flow, and selectable switches connected in circuit with each of the transistors. Selectable switches are actuable to produce an output trimming current of a desired magnitude, which current is used to correct the untrimmed stage output. The invention includes circuitry for controlling the polarity of the trimming current relative to the stage, and for selectively expanding or contracting the trimming range to optimize the trimming currents for the particular characteristics of the converter. A favorable balance between trimming accuracy and the area occupied by the trimming circuitry is attained by the use of both emitter-scaled and multicollector transistors in the trimming circuits.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.