A variable gain RF front-end, based on a voltage-voltage feedback LNA, for multistandard applications

Employing feedback circuits in RF front-ends can be
a key aspect for easy reconfiguration of multistandard receivers. A
narrow-band filter can shape the frequency transfer function and,
by reflection due to the feedback network, the input impedance.
Switching one single filter component thus allows selecting a
different standard. We introduce a voltage–voltage feedback low
noise amplifier that, besides being easily reconfigurable, shows
roughly the same noise and better linearity, for same power consumption,
as the conventional inductively degenerated topology.
A direct conversion front-end, including the LNA and and
mixers, tailored to WLAN applications in the 5–6 GHz range,
has been realized in a 0.25- m SiGe BiCMOS process. Prototypes
show the following performances: 2.5 dB NF, 31.5 dB gain,
9.5 dBm IIP3, and +23 dBm minimum IIP2 while consuming
16 mA from a 2.5 V supply.