CMOS LNA Operates In Subthreshold Region

BECAUSE THE LNA IS THE FIRST STAGE of a receiver system, an LNA's noise figure will dominate a receiver's overall performance. The LNA should therefore add little noise to the next stages while providing 50-O impedance match for maximum power transfer. It also should deliver enough gain for signal processing in the following stages. These goals were recently met by a 5.8-GHz, ISM-band, CMOS low-noise amplifier (LNA) that operates in a subthreshold region. The LNA was presented by Ickhyun Song, Hee-Sauk Jhon, Hakchul Jung, Minsuk Koo, and Hyungcheol Shin from Seoul's School of Engineering and Computer Science.

At the target frequency, the proposed LNA boasts measured signal gain of 13.4 dB and a 5.2-dB noise figure while consuming 980 W from a 1.8-V supply. The amplifier's forward gain is improved through the elimination of a source degeneration inductor. At the operating frequency, forward gain is 13.4 dB with a 5.2-dB noise figure. See "A Low Power Low Noise Amplifier with Subthreshold Operation in 130-nm CMOS Technology," Microwave And Optical Technology Letters, November 2008, p. 2762.