c 2008 Institute of Electrical and Electronics Engineers-A 24-GHz balanced amplifier (BA) with a 45-dB gain is realized in 0.18-mu m CMOS technology. An effective technique, pi-type parallel resonance, is proposed to boost the high-frequency gain of a MOSFET by resonating out the inherent capacitances. The miniaturized lumped-element coupler in the circuit occupies a chip area of only similar to 2% compared to that of the conventional transmission-line coupler. The BA consumes 123 mW from a supply voltage of 1V. To the best of the authors' knowledge, the proposed CMOS BA presents the highest gain of 45.0 dB with a chip area of 0.97 x 0.63 mm(2) (core area: 0.78 x 0.43 mm(2)) among the published narrowband amplifiers with similar technologies and operation frequencies.