A Self-Tuned Balun-LNA With Differential Imbalance Correction and Blocker Filtering

A CMOS self-tuned low noise amplifier (LNA) with single-to-differential function is presented. A tuned LNA with high-Q band-pass filtering is reconfigured to an oscillator simply by enabling a positive feedback buffer. Using the proposed LNA, an RF filter can be self-tuned without additional tone-generator circuits, and the calibration system is greatly simplified. By adopting a differential hybrid voltage buffer, differential imbalance is minimized. For a proof-of-concept, the proposed LNA is implemented using a 0.18 μm CMOS process. The circuit operates in a tuning range of 0.8-1.5 GHz, while the error between oscillation and center frequency is less than 5%. A pass band gain of 26.7-30 dB, a noise figure (NF) of 3.9-4.3 dB, and an in/out band IIP3 of -9.9/+10.6 dBm are obtained. The LNA consumes 9 mA with 1.8 V supply.