The Design of Narrowband CMOS RF Low-Noise Amplifiers

Abstract

General conditions for minimizing the noise figure of any linear two-port are reviewed before considering the specific case of a MOSFET low-noise amplifier (LNA). It is shown that the minimum noise figure cannot be obtained over an arbitrarily large bandwidth with networks of low order. For narrowband operation, however, one may construct simple amplifiers whose noise figure and power gain are close to the theoretical optima allowed within an explicit power constraint, and which simultaneously present a specified impedance to the driving source. The effects of overlap (drain-gate) capacitance, short-channel carrier heating, substrate resistance (“epi noise”), and gate interconnect resistance are also considered. Amplifier noise figures of 1.5dB or better at 10mW are achievable in the 1–2GHz range with 0.5μm technology, and improve with scaling.