A Low Noise Figure Rail-to-Rail Variable-Gain LNA for 900-MHz LoRa Application in 65nm CMOS Technology

This paper presents a low noise figure (NF) variable-gain low noise amplifier (VG-LNA) for the Long-Range (LoRa) Application. In the proposed circuit, a gain-cascaded branch is utilized to provide a rail-to-rail control voltage to vary the gain of LNA in a wide range and improve the dynamic range of the front-end LoRa receiver block. Besides, the proposed LNA’s gain is amplified using a current reused technique. The functionality of the suggested VG-LNA is assessed by the post-layout simulation results provided by TSMC 65 nm CMOS technology with a 1.2 V supply voltage. The simulation results demonstrate that the circuit’s gain is varied linearly from 7dB to 21dB by changing the control voltage from rail-to-rail. Besides, the proposed VG-LNA has an NF of less than 1.8 dB and S11 of better than -14 dB in a wide temperature range, while the power consumption is 6.8 mW @ 900 MHz. Also, the occupied area of the VG-LNA is 0.819 mm 2 ( 910 µm× 900µm).