AC Analysis of Differential Active Balun Topology

The current manuscript aimed to study a differential active balun circuit in terms of the small-signal analysis, implemented in a standard 90-nm complementary metal-oxide semiconductor (CMOS) technology. Small-signal or alternating current (AC) response or frequency response of the active balun determines the maximum frequency of operation and the effective bandwidth of the circuit. With the analysis, the active balun circuit could be modeled and designed to achieve gain or attenuation at the desired frequency of operation. Design tradeoffs are inevitable and are carefully considered in the analysis and design. Eventually, the differential active balun design achieved a gain difference better than 1 dB and a phase difference of 180°±10° or better at the frequency of operation of 5.8 GHz, comparable to previous designs and researches.