A 0.45-V low-power low-noise amplifier using a wideband image-rejection technology

A 0.45-V low-power wideband image-rejection low-noise amplifier (LNA) using Taiwan Semiconductor Manufacturing Company (TSMC) 0.18-μm CMOS process has been proposed. The supply voltage, power consumption and chip area of the proposed LNA can be reduced using forward body biasing, folded cascode topology and a feedback capacitor. Moreover, a wideband gain-enhancement-and-image-rejection (WGEIR) circuit including a variable resonant LC tank and a common-gate amplifier has been developed. The inductance of the variable resonant LC tank can enlarge the gain of the proposed LNA. The capacitance of the variable resonant LC tank can achieve the image rejection. Using the WGEIR circuit, gain enhancement and wideband image rejection can be achieved simultaneously. The variable inductors and capacitors are developed for suppressing wideband image signals and good image rejection ratio (IRR). The combination of the variable inductors and capacitors can achieve eight image-reject frequencies under three control voltages. The proposed LNA shows the measured results including a 10-dB power gain, a 3-dB noise figure (NF) and a −11-dBm input third-order intercept point (IIP₃) at 2.4 GHz, respectively. The measured IRR ranges from 18 to 23 dBc around 3.6–4.5 GHz, which is 900-MHz image-reject bandwidth. The measured proposed LNA using the mentioned techniques consumes 0.8-mW power.