Monolithic feedback low noise X-band amplifiers using 0.5-mu m GaAs MESFET's: Comparative theoretical study and experimental characterization

Abstract

Three different feedback low-noise-amplifier (LNA) circuit topologies for simultaneous noise and power matching are theoretically investigated and compared for the X-band application. The smallest minimum noise figure (NFmin) is shown to be achieved by the common source parallel feedback (CSPF) topology, while the common source series feedback (CSSF) topology exhibits the best overall performance, Experimentally, a CSSF three-stage LNA has been fabricated using 0.5-mu m-gate GaAs MESFET's and systematically characterized, In this LNA circuit, an optimal series feedback for noise figure, gain, and stability is implemented via a proper choice of the short stub length, The size of the fabricated monolithic microwave integrated LNA chip is only 1 mm(2)/stage, The measured gain varies from 22.0 to 23.0 dB in the frequency range of 8 to 10 GHz, with good flatness. The input/output voltage standing wave ratios are less than 2 and 1.43, respectively. The noise figure of the three-stage LNA is less than 2.6 dB, These measured data are sufficient for practical applications and are also in good agreement with simulated results.