A 12-bit cyclic analog to digital converter (ADC) used in long line array infrared sensors readout circuit is presented. The architecture of a low-power amplifier shared with two groups of switched capacitors is used to reduce power consumption. By adding cross-connected switches, the amplifier's offset is effectively canceled out. The improved redundant signed digit (RSD) correction technique is employed to compensate for the error resulting from the comparator's offset in sub-ADC, and the correction technique can tolerate high level of switched capacitor mismatch error, as well. The converter manufactured with Chartered 0.35 μm CMOS process exhibits 0.92 LSB maximum differential nonlinearity (DNL) and 1.5 LSB maximum integral nonlinearity (INL). The ADC has a 69.3 dB signal to noise and distortion ratio (SNDR) at 250 kS/s sample rate and 3 MHz clock frequency. It dissipates 0.8 mW with 3.3 V supply and occupies 0.22 × 0.9 mm2.