A 100-MHz — 5.0-GHz active balun using 0.18-µm CMOS process

A 100-MHz to 5.0-GHz broadband active balun using 0.18-μm CMOS process is presented in this paper. This active balun is made up of a current reusing common-drain and common-source stage and a differential stage. Because of the symmetrical architecture and identical parameters of the four PMOS transistors, the transconductances and output resistances of the common-drain and the common-source amplifiers are the same. Power consumption decreases through current reuse, and the final output amplitude and phase imbalance improves. Besides, a PMOS feedback is used to compensate the leakage of the common-drain amplifier to mitigate amplitude and phase imbalances. The simulated results show that from 100 MHz to 5.75 GHz, the two differential outputs can provide gain between +6.5 dB and 0 dB with less than 0.2-dB amplitude imbalances. Phase difference keeps an ideal 180-degree value below 4 GHz, and within just 6 degrees deviation till 5.0 GHz. And it consumes merely 1.4 mW from 1.2 V supply.