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Techniques are proposed to enhance the bandwidth of ultra-wideband (UWB) CMOS low-noise amplifiers (LNA). By using multiple-input-branch technique and resistive shunt- feedback technique, LNA could achieve ultra-wideband input impedance matching with small noise figure degradation. The gain bandwidth is enhanced by an L type inter-stage matching network between the input transistors and the cascode transistor which could enhance both the gain and the gain bandwidth. The gain bandwidth could be further enhanced by the resistors inserted between the bulks and the sources of the input transistors since the resistors could reduce the effects of the drain-bulk capacitance of the input transistors. The techniques proposed offer the advantages of ultra-wideband bandwidth, simple circuit topology, and small chip area. The proofs of techniques are demonstrated by designing the UWB LNA in UMC 0.18um CMOS.
Date of Conference: 18-21 May 2008