A Single-Ended-to-Differential Low-Noise Amplifier With Transformer-Based Feedback Network for 3–5 GHz UWB Applications

A wideband single-ended-to-differential (S-to-D) low-noise amplifier (LNA) for ultra-wideband (UWB) wireless sensors and internet-of-things applications is presented. In order to simultaneously provide wideband input matching characteristics, low-noise performance, and flat in-band gain response, a common-source input stage with on-chip transformer-based reactive feedback network is proposed. With the use of an on-chip transformer that serves as a shunt peaking inductor in differential mode, the LNA achieves improved voltage gain at high frequencies. At the input port, a cross-coupled common-gate stage balances the currents in differential operation, minimizing the gain and the phase mismatches at the differential output node. The proposed S-to-D LNA fabricated in a commercial 180 nm bulk CMOS technology exhibits a peak gain of 10.5 dB, an in-band minimum noise figure of 3.6 dB, and an input return loss of better than 8.8 dB from 3.0 GHz to 5.0 GHz, and a power consumption of 5.5 mA from a 1.8 V dc supply. The measured amplitude and phase mismatches are within 0.2 dB and 2.3 degrees, respectively. In comparison with other state-of-the-art designs, the proposed S-to-D LNA achieves low amplitude and phase mismatches, demonstrating well-balanced performance for 3–5 GHz UWB applications.