The present invention discloses a photosensitive circuit comprising a photosensitivity unit, a capacitance and a switch unit. The photosensitivity unit is capable of receiving a received light, and the capacitance is capable of storing a photoelectric current corresponding to the received light. The switch unit is used to respectively provide the positive voltage of the capacitance to a comparison unit at a first time period, and the negative voltage of the capacitance to a comparison unit at a second time period. The comparison unit outputs a detection value according to the positive voltage and the negative voltage of the capacitance, the detection value is related to the distance between an object and the photosensitive circuit. The present invention further disclose a photosensitive chip to drive a luminescent unit to provide a detective light. The photosensitive chip comprises a sampling clock generator, the ambient light sensor unit, a proximity sensor unit and a driving clock generator.