A 2–40 GHz Active Balun Using 0.13 $mu{rm m}$ CMOS Process

A 2 to 40 GHz broadband active balun using 0.13 $mu{rm m}$ CMOS technology is presented in this letter. Using two-stage differential amplified pairs, the active balun can achieve a wideband performance with the gain compensation technique. This active balun exhibits a measured small signal gain of ${0} pm{1}~{rm dB}$, with the amplitude imbalances below 0.5 dB and the phase differences of ${180} pm {10} ^{circ}$ from 2 to 40 GHz. The core active balun has a low power consumption of 40 mW, and a compact area of 0.8 mm $times,$ 0.7 mm. This proposed balun achieved the highest operation frequency, the widest bandwidth, and the smallest size among all the reported active baluns.