|
PatentVote.com: Vote on your favourite invention!
|
|
 |
Title: Selectable trimming circuit for use with a digital to analog converter
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.
Other info: Inventors: Comer, Donald T. (Los Gatos, CA, US) Dooley, Daniel J. (Saratoga, CA, US) Schoeff, John A. (Los Gatos, CA, US) Application Number: 768328 Filing Date: 1977-02-14 Publication_date: 1979-02-06 Assignee: Precision Monolithics, Inc. (Santa Clara, CA) Primary Class(es): 341/121 327/405, 341/133 Other Classes: US Patent Ref:
Other Refs: Other References: The Engineering Staff of Analog Devices, Inc., Analog-Digital Conversion Handbook, 1972, pp. I-54 to I-63, II-40 to II-45, II-64 to II-77. Erdi, A Precision Trim Technique for Monolithic Analog Circuits, 1975 IEEE International Solid-State Circuits Conference, pp. 192, 193, Digest of Technical Papers. The Engineering Staff of Analog Devices, Inc., Analog-Digital Conversion Handbook, 6/1972, pp. II-61 to II-63. | |