?2 infrared focal plane array (IRFPA) detector, whichconsist of reference resistor, detector resistor, reset switch, integrated capacitor and operational amplifier. Proposed ROICis designed using 0.35m 2P-4M (double poly four metal) n-well CMOS process parameters. Low noise folded cascodeoperational amplifier which is a key element in the ROIC showed 12.8 MHz unity-gain bandwidth and open-gain 89 dB,phase margin 67o, SNR 82 dB. From proposed circuit, we gained output voltage variation 17 mV/oC when the detectorresistor varied according to the temperature.