Patent ID: 11892327
Assignee: SEOUL NATIONAL UNIVERSITY R&DB FOUNDATION
Field: Measurement (Instruments)
Classification: CPC G  H | IPC G

Claim 4:
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.