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This paper explores the use of active feedback to boost the transconductance of a common-gate (CG) low-noise amplifier and achieve simultaneous low noise and input power match. Unlike transformer coupled topologies, the CG input stage is dc-coupled to a self-biased common-source feedback amplifier (for gm boosting), thus eliminating the need of external bias circuitry. Noise and intermodulation analysis with and without gm boosting are extensively studied yielding closed-form expressions of the noise figure (NF) and third-order input-referred intercept point (IIP3) that are useful for circuit design and optimization. A 9.6-GHz differential prototype implemented in a 0.18-mum technology using only NMOS transistors, achieves a minimum NF of 4 dB, an IIP3 of -11.3 dBm, a return loss of -17 dB, and a transducer gain of 18 dB while dissipating 10 m (excluding buffer circuit) from a 1.8-V supply voltage. The active chip area is 0.11 mum2.
Microwave Theory and Techniques, IEEE Transactions on (Volume:57 , Issue: 3 )
Date of Publication: March 2009