Presented is a 100 GHz fully differential CMOS passive imager for system-on-chip integration, which features high gain, high sensitivity and high resilience to flicker noise and gain variation. It integrates a low-noise amplifier, a Dicke switch, a detector and a baseband programmable gain amplifier in a single chip, and achieves the best noise equivalent power (NEP) (23fW /√(Hz)/26fW /√(Hz) for without/with Dicke switch) in CMOS, the highest responsivity (>;100 MV/W) in silicon. It also demonstrates 1.96 K noise-equivalent temperature difference in 30 ms integration time.