A compact and low power consumption three-stage differential K-band low-noise amplifier (LNA) with a 10dB differential mode gain at 25.8GHz and a 3dB bandwidth of 22.8-26.8GHz by using a transformer feedback technique with standard 0.18m CMOS technology is presented. The minimum input and output return losses over a 3dB bandwidth are 11 and 7dB, respectively. Fully differential characterisations of the noise figure (NF) and the common mode rejection ratio (CMRR) are demonstrated. The obtained NF and CMRR are 4.84dB and 23.3dB at 25.8GHz. The input 1dB compression point and input third-order intercept point are -17.8 and -5dBm, respectively. The overall power consumption is <25.6mW. This three-stage differential LNA only occupies an area of 0.63×0. 88mm2.