A 2.4 GHz Reconfigurable Cascode/Folded-Cascode Inductive Source Degenerated LNA With Enhanced OP1dB and OIP3 Over Gain Reduction
Dongmyeong Kim, Donggu Im
Abstract
A 2.4 GHz reconfigurable cascode/folded-cascode inductive source degenerated LNA (ISDLNA) is proposed to implement the variable-gain functionality with enhanced output 1 dB compression point (OP1dB) and output third-order intercept point (OIP3) over the gain reduction, ensuring low noise figure (NF) of sub-1 dB at high gain mode. Depending on the channel condition, the LNA is designed to be operated as the cascode and folded-cascode ISDLNA through the digital switch control to have low NF of around 1 dB at high gain mode and high input P1dB (IP1dB) of greater than −5 dBm at low gain mode, respectively. To avoid the reliability issues caused by the overdriving control voltage of greater than the nominal supply voltage, the transmission gate switch is employed as the common gate stage of the cascode amplifier. In experiments, the proposed variable-gain LNA shows a power gain <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$(S_{21})$ </tex-math></inline-formula> , input return loss <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$(S_{11})$ </tex-math></inline-formula> , and NF of 11.8 dB, −31.8 dB, and 1.1 dB at high gain mode, and 5.0 dB, −14.4 dB, and 1.96 dB at low gain mode. In case of the linearity, the proposed LNA shows an IP1dB and input IP3 (IIP3) of −19.2 dBm and −5 dBm at high gain mode, and −5.1 dBm and +4.8 dBm at low gain mode, respectively. The power consumption for two operation modes is the same as 9.6 mW from a 1.2 V supply voltage.