A low-cost 80×60 microbolometer CMOS (complementary metal-oxide-semiconductor) thermal imager is presented. The imager system integrated with a proposed 12-b biasing digital-to-analog converter (DAC) has 100 ms start-up time, which is 300× faster than commercial products, while ensuring comparable 100 mK noise-equivalent temperature difference. The low-noise biasing DAC adopts a current-mode divider-stacking structure and a bit-inversion technique, leading to mismatch-insensitive operation. The 12-b biasing DAC in a 0.18 μm CMOS imager IC has a low noise of 1.89 μV_rms and INL (integral non-linearity)/DNL (differential non-linearity) of 0.14/0.09 LSB, respectively.