Resistive-Feedback CMOS Low-Noise Amplifiers for Multiband Applications

Extremely compact resistive-feedback CMOS low-noise amplifiers (LNAs) are presented as a cost-effective alternative to multiple narrowband LNAs using high-Q inductors for multiband wireless applications. Limited linearity and high power consumption of the inductorless resistive-feedback LNAs are analyzed and circuit techniques are proposed to solve these issues. A 12-mW resistive-feedback LNA, based on current-reuse transconductance boosting is presented with a gain of 21 dB and a noise figure (NF) of 2.6 dB at 5 GHz. The LNA achieves an output third-order intercept point (IP3) of 12.3 dBm at 5 GHz by reducing loop-gain rolloff and by improving linearity of individual stages. The active die area of the LNA is only 0.012 mm². A 9.2-mW tuned resistive-feedback LNA utilizing a single compact low-Q on-chip inductor is presented, showing an improved tradeoff between performance, power consumption, and die area. At 5.5 GHz, the fully integrated LNA achieves a measured gain of 24 dB, an NF of 2 dB, and an output IP3 of 21.5 dBm. The LNA draws 7.7 mA from the 1.2-V supply and has a 3-dB bandwidth of 3.94 GHz (4.04-7.98 GHz). The LNA occupies a die area of 0.022 mm². Both LNAs are implemented in a 90-nm CMOS process and do not require any costly RF enhancement options.