CMOS Read-Out IC (ROIC) for the micro Bolometer type Infrared Sensor is to estimate voltage or current when resistance in bolometer sensor varies as infrared light radiates. Implemented ROIC patterns cannot be exactly same with LAYOUT pattern CMOS Read-out IC process. Also each bolometer pixel resistance is variable by process variation in uncooled Infrared Sensor process. Bolometer sensor is not only heated by the incident IR, but also by current flowing through it, which generates the bias-heating noise. In this paper, we present CMOS Read-out IC which used a fully differential input stage to reduce process variation and bias heating noise problems. We designed and fabricated a prototype readout integrated circuit intended for uncooled bolometer infrared focal plane array. The design is demonstrated by the fabrication of a prototype consisting of an array of 32 × 32 pixels. The prototypes are fabricated in 0.25 μm CMOS process.