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:
Nov. 02, 1999
Filed:
Aug. 19, 1997
Masahiro Tsugai, Toyko, JP;
Mitsubishi Denki Kabushiki Kaisha, Tokyo, JP;
Abstract
In an interface circuit connected to a capacitance type sensor having two sets of capacitors C1 and C2 whose capacitances are varied, this interface circuit is equipped with an OP amplifier A1 where a feedback/sampling capacitor C3 is connected between its output terminal and its inverting input terminal; and a holding capacitor C4 connected between a non-inverting terminal of the OP-amplifier A1 and a reference voltage source; one ends of the respective capacitors C1, C2, C3 are connected to the inverting input terminal of the OP amplifier A1; at timing .phi.1 of a switching cycle, the other ends of the respective capacitors C1, C2 are connected to a power source and the capacitor C3 is shortcircuited; at timing .phi.2 thereof, the other ends of the capacitors C1, C2 and an output terminal of the OP amplifier A1 are connected to the non-inverting input terminal of the OP amplifier A1; and the switched capacitor type interface interface circuit further includes: a multiplexer for sequentially connecting a plurality of the capacitance type sensors to the capacitance type sensor interface circuit in a second switching cycle having a time period longer than time periods of the switching cycles .phi.1 and .phi.2; and a plurality of sample/hold circuits whose quantity is equal to those of the plural capacitance type sensors, which are sequentially connected to the capacitive type sensor interface circuit in response to the connections of the plural capacitance type sensors in the second switching cycle.