Apparatus for sensing a touch

An apparatus for sensing a touch comprising:

• a first amplifier having a first input terminal and a second input terminals configured to output a difference of a first input voltage applied to the first input terminal and a second input voltage applied to the second input terminal;
• a second amplifier configured to amplify and output the difference from the first amplifier;
• a converting unit configured to convert the output from the second amplifier into a digital signal and output the digital signal;
• and
• a control unit configured to receive the digital signal from the converting unit and output a control signal which adjusts impedance of the second input terminal;
• and
• a filter configured to remove a noise component from the output of the second amplifier,
• wherein the apparatus is configured for operation between a calibration mode to adjust impedance of the second input terminal and a scan mode to scan a touch and touch sensitivity at the first input terminal, such that in the calibration mode, the control unit is configured to store the digital signal from the converting unit as an error code, and in the scan mode, the control unit is configured to detect a change of a voltage applied to the first input terminal from a result of comparing the output from the converting unit with reference to the error code stored in the scan mode.