An inductorless high linear UWB Cascode LNA with tunable active resistance feedback and post-linearization technique

An inductorless Cascode SiGe low noise amplifier (LNA) that achieves high linearity using tunable active feedback and post-linearization technique is proposed for ultra-wideband (UWB) application. Tunable active feedback composed of NMOS and parallel resistor is adopted to improve the linearity instead of the resistor feedback. The tunablity of active feedback can compensate the gain and bandwidth degradation due to the process variation and parasitic parameters. The post-linearization technique by the use of resistance-capacitance (RC) parallel network with an additional diode connected transistor further improves the linearity. Theoretical analysis is performed using Volterra series to obtain an insight into the linearity behavior over the UWB frequency range. The LNA is implemented using TSMC 0.35 μm SiGe BiCMOS technology. Compared with the conventional Cascode LNA, IIP3 of the proposed LNA is improved by 51 dBm. Meanwhile, the novel LNA exhibits superior variation of group delay 1 ps, and achieves the noise figure of 3.8∼4.9 dB, the gain of 8.8∼10.2 dB, gain flatness of ±0.7 dB, good input and output impedances matching, and unconditional stablity in the whole band.