A 3-to-5 GHz UWB LNA with a low-power balanced active balun

A 3-to-5 GHz ultra-wideband (UWB) low-noise amplifier (LNA) with a low-power balanced active balun aiming at IEEE 802.15.4a (Band Group 1) compliance is presented. The LNA employs an NMOS feedback for wideband input matching, and current reuse scheme for reducing power consumption. The active balun uses a differential amplifier with a cascoded cross-coupled pair to provide 6 dB gain as well as to mitigate the gain and phase imbalances. The proposed fully integrated LNA and balun achieve noise figure of 3.6 dB, S21 of 30 dB, and IIP3 of -24 dBm (-12 dBm for LNA core) from 3 GHz to 5 GHz. The maximum gain and phase mismatches of the balun from 0.5 GHz to 10 GHz are 0.4 dB and 1.8deg, respectively. It consumes 19 mW from 1.2 V supply; 8 mW for the LNA, 2.5 mW for the active balun, and 8.5 mW for the buffer.