A 5.2GHz variable gain low noise amplifier RFIC with adaptive biasing for improved linearity

This paper presents a 5.2-GHz adaptively-biased variable gain- low noise amplifier (VG-LNA) using SiGe BiCMOS technology. Usage of bias and gain control simultaneously to achieve high input-referred third-order intercept point (IIP3) is demonstrated. A charge pump is used to transform the RF output signal of LNA to dc control signal. Measurement results show that with 3.3V power supply, the LNA exhibits a tunable bias from 3mA to 10.85mA with gain tuning range of 13dB, and a 14.5dBm IIP3 improvement. In the high gain mode, the noise figure of 2.82 of the LNA is achieved.