A 0.4-V High-Gain Low-Noise Amplifier Using a Variable-Frequency Image-Rejection Technology

A 0.4-V high-gain low-noise amplifier (LNA) using a variable-frequency image-rejection technology in Taiwan Semiconductor Manufacturing Company (TSMC) 0.18-mu m CMOS process has been proposed. By using forward body biasing and folded topology, the supply voltage and power consumption can be reduced. For achieving low power consumption and small chip area, a feedback capacitor is used to shrink the size of the inductors of the input impedance matching. Moreover, a gain-enhancement-and-image-rejection (GEIR) circuit including an inductor and a variable capacitor is proposed for achieving GEIR simultaneously. The image-rejection frequency can be altered for avoiding strong image signals by the variable capacitor. The proposed LNA shows the measured results including a 15-dB power gain, a 2.6-dB noise figure, and a -13-dBm input third-order intercept point at 2.4 GHz, respectively. And the measured variable image rejection ratio ranges from 14 to 39 dBc around 3-3.6 GHz for avoiding strong image signals. The measured P-dc is 0.8 mW.