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:
Aug. 17, 2004
Filed:
Jan. 28, 2003
D/a converter circuit, and portable terminal device and audio device using the d/a converter circuit
Hirofumi Matsui, Kashiba, JP;
Sharp Kabushiki Kaisha, Osaka, JP;
Abstract
A first D/A converter generates first and second reference voltages from digital data of upper m bit by using base reference voltages of these reference voltages. A controller outputs a control signal according to which of voltage levels of the first and second reference voltages is higher. An inversion controller outputs digital data of lower n bit as such to a second stage R-2R ladder resistor type D/A converter when judging that the first reference voltage is higher in voltage level than the second reference voltage, and outputs the digital data of the lower n bit to the second stage R-2R ladder resistor type D/A converter by inverting the digital data of the lower n bit when judging that the first reference voltage is lower in voltage level than the second reference voltage. The second stage R-2R ladder resistor type D/A converter uses the digital data inputted from the inversion controller to operate switches for switching the first and second reference voltages, and outputs an analog output voltage value corresponding to digital input data. On this account, it is possible to provide a D/A converter circuit of plural stages capable of easily ensuring uniformity and continuity of the output analog voltage value, and further capable of obtaining high D/A conversion accuracy.