This paper presents a Q-band balanced medium power amplifier fabricated using standard 90-nm 1P9M CMOS technology. The balanced amplifier, which is constructed with two broadband amplifiers and two broadside couplers using thinfilm microstrip (TFMS) line technique, has a compact chip size of 0.78 x 0.92 mm2. The MMIC demonstrates a measured gain of 14.5 dB at 48 GHz. With the feature of the balanced amplifier, the MMIC has a 3-dB bandwidth up to 37.2 % from 35 to 51 GHz with flat gain and return loss frequency response. Furthermore, the balanced amplifier delivers a saturation output power of 10.6 dBm with 8% PAE and OPldB is 7.5 dBm.Index Terms -Millimeter-wave (MMW), Q-band, CMOS, balanced amplifier, thin-film microstrip (TFMS), broad-side coupler.