A DC-10 GHZ HIGH GAIN-LOW NOISE GAAS HBT DIRECT-COUPLED AMPLIFIER

An AlGaAs/GaAs HBT wide-band low noise amplifier has been achieved usi ng a direct-coupled amplifier topology, A nominal gain of 22.5 dB and a noise figure of 3.0-3.65 dB has been achieved over a dc-10 GHz band, while consuming less than 55 m W of de power through a 5 V supply, Th is result benchmarks the lowest noise figure so far reported for a dir ect-coupled HBT amplifier at X-band frequencies, In addition, an appro ximate expression for the amplifier noise figure is given that predict s the noise figure to within 0.3 dB over bias and frequency, The ampli fier can be compacted into a 0.3 x 0.3 mm(2) area and can yield as man y as 30 000 die per 3-in. GaAs wafer. The broadband gain and noise fig ure, low de power, and miniature die size makes this design attractive as a standard off-the-shelf microwave product for high volume commerc ial applications.