Verfahren zur Bestimmung sehr kleiner Kapazitäten und Verwendung

摘要

A raster of condenser surfaces is connected to read and control lines. The read lines (LL) are connected to the output of a feedback operational amplifier (OP) and a central condenser (Cs). The capacitance (Cp) to be measured is charged several times and the charges are collected on the central condensers. The potential on the read lines are kept constant using the low impedance output of the operational amplifier between charges. The utilization of said method in a fingerprint sensor makes it possible to evaluate all read lines.