The background output of the PbS detector is determined by the ratio of the resistance of the detector to that of the reference at the input of the readout circuit. The performance of 1×128 linear photoconductive (PC) PbS infrared focal plane arrays (IRFPAs) was improved by tuning the resistance of the detector with laser. The background out-put of IRFPAs is reduced by tuning the resistance of the detector. As a result, the average responsivity and detectivity of the detector is increased from 4.45×106 V/W to 8.82×106 V/W, and 6.52×109 cm·Hz1/2·W-1 to 1×1010 cm· Hz1/2·W-1, respectively. The dynamic range is also increased from 46 dB to 52dB.