Design and implementation of a differential LNA for WiMAX system

The low noise and high gain differential Low Noise Amplifier (LNA) was designed for an IEEE 802.16 Worldwide Interoperability Microwave Access (WiMAX) application. This paper presents a 3.3 GHz to 3.8 GHz CMOS LNA with differential and cascode circuits to reduce the noise figure (NF) and enhance the gain. The LNA was fabricated with Taiwan Semiconductor Manufacturing Company (TSMC) 0.18 ¿m 1P6M standard CMOS process, the cascode technique can reduce the miller effect of gate-drain capacitor C_gd in order to enhance gain, and the active balun can enhance gain and reduce noise. The circuit performances were measured by using on-wafer test. The differential LNA exhibits that the noise figure is 3.3 dB ~ 3.8 dB from 3.3 GHz to 3.8 GHz, the maximum power gain S₂₁ is 14.4±0.6 dB and S₃₁ is 12.4 ± 0.5 dB. The output return loss S₂₂ and S₃₃ are less than -11 dB. The power consumption is 14.8 mW at V_DD=1.2 V.