A 2.4-GHz/5.25-GHz CMOS variable gain low noise amplifier using gate voltage adjustment

This paper presents a 2.4GHz/5.25GHz dual band two-stage differential low noise amplifier (LNA) with a variable gain which is implemented with 0.18-μm CMOS technology. In the proposed differential LNA, two cascode pairs are used to have low current and high isolation; and that two current-reused paths are presented to have low power consumption. Besides, the variable gain is completed by adjusting the gate voltages of MOSFETs, M3 and M7. Furthermore, a capacitor C2 is added to the gate of transistor M2 to have a stable bias voltage by filtering out the RF signal; and that a differential mode is considered to have good linearity and high gain. The simulation results present that the gain varies from 16.66 dB to 19.89 dB at 2.4 GHz, whereas the gain varies from 2.63 dB to 16.33 dB at 5.25 GHz.