Patent attributes
A capacitance detecting circuit detects the variations of capacitances at intersections of a plurality of column lines and a plurality of row lines opposite to the column lines and then converts the variations of capacitances into electrical signals. The capacitance detecting circuit includes a column line driving means that drives the column lines, a comparator that is connected to the row lines to convert charges stored in capacitors formed at the intersections of the driven column lines and the row lines into a measured voltage, and that compares the measured voltage with a predetermined set value to output charging or discharging signals, a constant current source that performs charging or discharging on the charges in response to the charging or discharging signals, and a capacitor that stores charges by means of the charging or discharging current. In the capacitance detecting circuit, a voltage between both ends of the capacitor is output as the electrical signal.
