BiCMOS Variable Gain LNA at C-Band with Ultra Low Power Consumption for WLAN

An ultra low power consuming low noise amplifier (LNA) at C-band with variable gain for adaptive antenna combining is presented in this paper. The microwave monolithic integrated circuit (MMIC) was fabricated using commercial 0.25 μm bipolar complementary metal oxide semiconductor (BiCMOS) technology. At 5.2 GHz, a supply voltage of 1.2 V and a current consumption of only 1 mA, a maximum gain of 12.7 dB, a noise figure of 2.4 dB and a third order intercept point at the output (OIP3) of 0 dBm were measured. A large amplitude control range of 36 dB was achieved. To the knowledge of the authors, the obtained gain/supply power (S21/Pdc) figure of merit of 11 dB/mW is by far the highest ever reported for silicon based C-band LNAs. The characteristics of different bias methods for amplitude control of the cascode circuit are elaborately discussed. A bias control method is proposed to significantly decrease the transmission phase variations versus gain.