A 900-MHz 1.25-dB Noise-Figure Differential-Output LNA with 12.5 dB/mW FoM

A 900 MHz LNA with balanced output and 12.5-dB/mW figure-of-merit (FoM) is presented. The architecture exploits the benefits of both inductive degeneration and noise cancellation which helps in achieving the optimum noise figure (NF). The LNA has a wideband gain and input matching is achieved using an off-chip inductor. Inductive degeneration and quality factor (Q) of the input matching network improves the NF of the LNA (with wideband gain) at a spot frequency. The transconductance of the core-LNA is fixed by a constant-gm circuit. Simulation results show that the LNA has a minimum NF of 1.25 dB at 900 MHz, transmission gain (S21) of 33 dB, S11 of −19 dB at 900 MHz, IIP2 of +2 dBm, and IIP3 of −15 dBm. The LNA, designed in 180 nm CMOS, consumes 4.4 mA from a 1.8 V supply and has a negligible differential-gain error of 0.138 dB, at the input matched frequency. A 2.5-dB NF balanced passive mixer on top of the LNA is also implemented.