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:
Jun. 20, 1995
Filed:
Nov. 09, 1993
Kazuo Ryu, Tokyo, JP;
NEC Corporation, Tokyo, JP;
Abstract
Disclosed is an analog/digital (A/D) converter, which comprises an M-bit resistor-string type digital/analog (D/A) converter, a charge re-distribution type N-bit D/A converter, a comparator, a successive approximation register for storing the output of the comparator, and first and second switch controllers for respectively controlling the two D/A converters in accordance with the output of the successive approximation register. The N-bit D/A converter uses voltages at both ends a and b of an arbitrary unit resistor of the resistor string of the M-bit D/A converter as reference voltages. The comparator has a differential amplifier whose one input terminal is connected to a capacitor for sampling an analog input signal. The output of the N-bit D/A converter is connected to the other input terminal of the differential amplifier. As the differential amplifier is used in the comparator and the N-bit D/A converter of a charge re-distribution type is used instead of a resistor-string type, the number of components and the area of the A/D converter can be reduced considerably. Even if the number of bits increases, therefore, an increase in pellet area will be suppressed.