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:
Jan. 21, 2014
Filed:
May. 06, 2011
Hiroaki Shirai, Kanagawa, JP;
Hiroaki Shirai, Kanagawa, JP;
Renesas Electronics Corporation, Kawasaki-shi, Kanagawa, JP;
Abstract
An impedance detection circuit includes a detection circuit, a correction circuit, a subtraction circuit, and an AC signal generator. The detection circuit has a first operational amplifier having an inverting input terminal coupled with one end of a signal line to whose other end a measured capacitor Cs is coupled, a non-inverting input terminal coupled with a shielding wire covering at least a part of the signal line and an output terminal of the AC signal generator, and an output terminal, and a second feedback resistor coupled between the output terminal and the inverting input terminal of the first operational amplifier. The correction circuit has a third resistor and a variable capacitor, and corrects a detection signal outputted from the first operational amplifier by adjusting a capacitance of the variable capacitor.