Offset canceling circuit, sampling circuit and image sensor

PURPOSE: An offset cancelling circuit, a sampling circuit, and an image sensor are provided to eliminate offset between unit cells. CONSTITUTION: A decoupling capacitor(110) includes a first electrode and a second electrode connected to a unit cell(200). The unit cell outputs a reset voltage and a data voltage. A buffer(120) is connected to the second electrode. A feedback circuit(130) receives a reference voltage. The feedback circuit is connected to the second electrode and an output terminal of the buffer. The feedback circuit provides the reference voltage to the second electrode to charge charges corresponding to a first voltage in the decoupling capacitor. The first voltage is the difference between the reset voltage and the reference voltage.