A Digitally Controlled Variable-gain Low-noise Amplifier with Strong Immunity to Interferers

A variable-gain low-noise amplifier with capacitive step attenuators is presented. The gain is digitally controlled by current splitting technique of cascode transistors for linearity requirements. The fabricated LNA showed IIP3 increase of -1.1 to 3.5 dBm at gain of 25.8 to 21.2 dB, respectively, wide gain range of over 42.7 dB by capacitive attenuators, NF of 1.5 dB at 650 MHz, and power consumption of 15.4 mW with 2.9 V supply voltage using a 0.5-mum BiCMOS process.