A DC-coupled Active Balun with 28 GHz Bandwidth and 0.3 dB-3.5°Amplitude - Phase Error in 40-nm CMOS

This paper presents a DC-coupled active balun fabricated in a $40-\mathrm{nm}$ CMOS technology. A wideband phase and amplitude correction technique based on auxiliary baluns is employed, minimizing the phase and amplitude errors. Interwound T-coil peaking is utilized to extend the bandwidth. The measured balun achieves 8.2 dB single-ended to differential gain with 28 GHz 3-dB bandwidth. Peak phase and amplitude error of 4 degrees and 0.3 dB within the bandwidth, respectively. The measured minimum noise figure is 4.4 dB. The measurement results show that the designed balun is suitable for high-speed, high-bandwidth baseband applications.