Patent ID: 7667501

Claim:
An apparatus comprising: a charge-to-voltage converter having: a first operational amplifier having a first input terminal, a second input terminal, a first output terminal, and a second output terminal; a first capacitor that is coupled to the first input terminal of the first operational amplifier and the first output terminal of the first operational amplifier; a second capacitor that is coupled to the second input terminal of the first operational amplifier and the second output terminal of the first operational amplifier, wherein the capacitance of the first capacitor is approximately equal to the capacitor of the second capacitor; a third capacitor that is coupled to the first input terminal of the first operational amplifier; a fourth capacitor that is coupled to the second input terminal of the first operational amplifier, wherein the capacitance of the third capacitor is approximately equal to the capacitance of the fourth capacitor; a first switch that is coupled between the third capacitor and the first output terminal of the first operational amplifier; a second switch that is coupled between the fourth capacitor and the second output terminal of the first operational amplifier; a third switch that is coupled between the third capacitor and ground; and a fourth switch that is coupled between the fourth capacitor and ground; and a correlated double sample (CDS) amplifier having: a second operational amplifier having a first input terminal, a second input terminal, a first output terminal, and a second output terminal; a fifth capacitor that is coupled to the second input terminal of the second operational amplifier and to the first output terminal of the first operational amplifier; a sixth capacitor that is coupled to the first input terminal of the second operational amplifier and to the second output terminal of the first operational amplifier, wherein the capacitance of the fifth capacitor is approximately equal to the capacitance of the sixth capacitor; a third switch that is coupled to the first output terminal of the second operational amplifier; a fourth switch that is coupled to the second output terminal of the second operational amplifier; a fifth switch that is coupled to the first input terminal of the second operational amplifier; a sixth switch that is coupled to the second input terminal of the second operational amplifier; a seventh capacitor that is coupled between the third and fifth switches; and an eighth capacitor that is coupled between the fourth and sixth switches, wherein the capacitance of the seventh capacitor is approximately equal to the capacitance of the eighth capacitor, and wherein the ratio of the capacitance of the third capacitor to the capacitance of the first capacitor is approximately equal to the ratio of the capacitance of the fifth capacitor to the capacitance of the eighth capacitor.