The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 12, 1981
Filed:
Jan. 25, 1980
James B Cecil, Santa Clara, CA (US);
National Semiconductor Corporation, Santa Clara, CA (US);
Abstract
The disclosed digital to analog conversion circuit is comprised of a plurality of resistors interconnected as an N stage R-2R ladder network, a pair of conductive buses, and a total of N transistorized switches which respectively couple the output legs of the ladder to a selectable one of the buses in response to digital logic signals. Those switches which couple to the legs of the K most significant stages have scaled resistances that differ by powers of two; whereas the remaining switches have resistances which equal the largest scaled resistance. An MOS transistor lies in the serial leg of the Kth stage. This transistor has a resistance of approximately 2/3 the largest scaled resistance of the switches. The unscaled resistances provide for ease of fabrication, while the MOS transistor improves the accuracy with which digital to analog conversions are performed.