A fully-integrated SiGe wide band amplifier implemented in a standard low cost 0.35 &mgr;m 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. All this results were measured in a probe station.
In the last years, WIFI market has shown an incredible growth, exceeding expectations. This paper presents the design of two fully integrated LNAs using a low cost SiGe 0.35 um technology for the 5 GHz band, according to the IEEE 802.11a WIFI standard. One LNA has an asymmetric configuration and the other a balanced configuration. A comparison between the two LNAs has been made. All passives devices are on chip, including integrated inductors which have been designed by electromagnetic simulations. This work demonstrates the feasibility of a low cost silicon technology for the design of 5 GHz band circuits