Patent ID: 9594103
Date: 2017-03-14
CPC Classifications: B06B,B81C,G01D,G01N,G01R

Claim:
1. An apparatus comprising: a plurality of cells, each cell including (a) a first electrode, and (b) a second electrode opposed to the first electrode with a gap between the first and second electrodes; a plurality of detection circuits, each detection circuit being configured to detect a current output from a respective detection electrode that is one of the first and second electrodes; and an addition circuit for adding signals from the plurality of detection circuits, wherein the plurality of cells are classified into a plurality of groups, each group including at least two cells, wherein a plurality of the detection electrodes of the cells in one group are commonly connected to one detection circuit of the plurality of detection circuits, wherein the one detection circuit adds currents output from the plurality of the detection electrodes of the cells in one group and converts a current resulting from an addition of the currents output from the plurality of the detection electrodes of the cells in one group into a voltage, wherein the addition circuit adds respective voltages converted by the plurality of the detection circuits, wherein each detection circuit comprises a current-to-voltage conversion circuit including an operational amplifier, a feedback capacitance, and a feedback resistance, and wherein, a gain bandwidth of the operational amplifier is GBW, a resistance value of the feedback resistance is RF, a capacitance value of the feedback capacitance is CF, a parasitic capacitance of an inverting input terminal of the operational amplifier is Cin, following Expression (1) is met: