A 3-10 GHz ultrawideband SiGe LNA with wideband LC matching network

Abstract

A fully-integrated SiGe wide band amplifier implemented in a standard low cost 0.35 μm process up to 12 dB of gain and a bandwidth of 3-10 GHz is presented. This circuit is divided in 3 stages. The first one is the input matching where the use of an inductively degenerated amplifier is expanded by embedding the input network of the amplifying device in a multisection reactive network so that the overall input reactance is resonated over a wider bandwidth. The second stage is a cascode transistor to obtain a great power gain and a high isolation between input and output ports. In adition, by adjusting the area and the multiplicity of these transistors, we can reduce the noise figure of the circuit. Finally at the output a new technique is used to increase the bandwidth. This technique is based in the replacement of the load resistor by a shunt-peaking resistor composed by an inductor and a resistor. The addition of an inductance gives an output impedance that remains roughly constant over a broader frequency range. Chip dimensions are 0.665 × 0.665 mm2 and power dissipation is 39 mW, drawn from a 3.3V supply. The noise figure ranges from 3.5 to 7.5 in the band between 2 GHz and 8.5 GHz. Finally, the circuit core draws 5.3 mA from a 3.3-V supply. AU this results were measured in a probe station.