US 11,892,327 B2
Read-out circuit for a capacitive sensor
Minsung Kim, Gwacheon-si Gyeonggi-do (KR); Hyunjoong Lee, Daejeon (KR); and Suhwan Kim, Seoul (KR)
Assigned to Seoul National University R&DB Foundation, Seoul (KR)
Filed by Seoul National University R&DB Foundation, Seoul (KR)
Filed on May 31, 2022, as Appl. No. 17/828,269.
Claims priority of application No. 10-2021-0072317 (KR), filed on Jun. 3, 2021.
Prior Publication US 2022/0390259 A1, Dec. 8, 2022
Int. Cl. G01D 5/24 (2006.01); G01R 27/26 (2006.01); G01R 29/08 (2006.01)
CPC G01D 5/24 (2013.01) [G01R 27/2605 (2013.01); G01R 29/0871 (2013.01)] 19 Claims
OG exemplary drawing
 
5. A read-out circuit comprising:
an operational amplifier configured to receive an input voltage through a positive input terminal;
a feedback capacitor connected between an output terminal and a negative input terminal of the operational amplifier;
a sensor charging and discharging circuit configured to charge or discharge a sensor during a first time;
an offset cancelling circuit having an offset capacitor connected between a first node and a second node and configured to charge or discharge the offset capacitor during the first time;
a first switching circuit configured to provide a power supply voltage or a ground voltage to the first node during the first time;
a second switching circuit configured to connect the operational amplifier with the offset cancelling circuit and to connect the offset cancelling circuit with the sensor during a second time after the sensor is charged or discharged; and
a duty control circuit configured to control a duty ratio of the first time and the second time according to capacitance of the sensor or capacitance of the offset capacitor.