Active balun using resistive feedback for low gain imbalance

Abstract

AbstractAn active balun using current steering topology is presented for phase and amplitude corrections. The proposed active balun is constructed with two different unit balun structures based on resistive feedback to reduce phase and amplitude errors. The first unit balun composed of the common source configuration provides a main transconductance stage for the proposed active balun. The second unit balun using common source and common gate configurations works for phase and gain error reduction. The resistive feedback proposed here leads to mitigation of phase error and then amplitude error, and an equation for deciding the feedback resistance is successfully deduced. The value of a feedback resistor is determined to provide the least phase and amplitude errors by optimizing the derived design equation. Designed and fabricated active balun in 65 nm CMOS process operates over 1.0–1.2 GHz band, showing input and output reflection coefficients under –10 dB, phase error under 3.5° and gain error under 1.4 dB over the frequency of interest. Moreover, the gain is measured to be 4 dB maximum and power consumption of 2.6 mW is measured.