A 0.3-3.5 GHz active-feedback low-noise amplifier with linearization design for wideband receivers

LNAs for wideband receivers usually require a high linearity to protect the desired signals from out-band interference. Active feedback LNAs always suffer from the nonlinear feedback of source follower, and present a poor linearity. In order to solve this problem, a complementary source follower (CSF) is proposed, which utilizes the different characteristic of NMOS and PMOS to linearize the source follower, leading to an improvement of LNA's IIP3 and IIP2 by about 10 dBm and 21 dBm respectively. In addition, a post-distortion technique is also used on the common source stage, which further enhances the IIP3 by about 2 dBm and IIP2 by 11 dBm. After using the two techniques, the noise figure (NF) does not deteriorate; instead it achieves a 0.3 dB improvement. A prototype is designed in TSMC 0.18 mu m CMOS process, and a 14.8 mW power is dissipated from a 1.6 V supply. In typical process corner, across 0.3 to 3.5 GHz, this LNA achieves a 14.6 dB gain, a 2.9 dB minimum NF, and an IIP2 larger than + 22 dBm and IIP3 larger than +1.2 dBm.