Fairchild Camera and Instrument Corp.

John P Guadagna

Kamleshwar C Gunsagar

Kenneth R Stafford

A balanced differential capacitively decoupled charge sensor for detecting small amounts of charge comprises balanced differential sensing means adapted to receive charge representing data and charge representing a reference value, a pair of capacitance decoupling transistors, the respective drains of each of said pair of capacitance decoupling transistors being electrically coupled to the respective inputs of said differential sensing means, a matched pair of charge output nodes electrically coupled to the respective sources of said capacitance decoupling transistors and adapted to receive, respectively, data charge and reference charge, and means for biasing and resetting both of said charge output nodes so that said capacitance decoupling transistors are functioning in a high transconductance mode when data charge and reference charge are received.

Balanced differential capacitively decoupled charge sensor

According to the invention, the electrical charge which is transferred to a circuit node by the switching ON or OFF of a field effect transistor whose source or drain is connected to that node is cancelled by connecting the source and drain of another field effect transistor to that circuit node and applying to its gate terminal a complement of the switching signal applied to the gate electrode of the first field effect transistor.

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San Jose, CA, United States of America

John P Guadagna