A single-stage cryogenic LNA with low power consumption using a commercial SiGe HBT

A cryogenically cooled low noise amplifier (LNA) has been designed, built and tested at the Astronomy Instrumentation Laboratory at Arizona State University. The LNA uses low cost, off the shelf commercially available low noise SiGe hetero junction bipolar transistor (HBT) in a single stage surface mount package. The built LNA has been measured in a calibrated noise/gain/S-parameters setup and the data shows the LNA has a noise temperature of as low as 5K (or about 0.074dB noise figure) and more than 20dB of Gain on the 100MHz-1GHz band. The input and output of the LNA are matched to 50 Ohm, an S11 and S22 of less than -10dB at most frequencies have been measured. All these parameters were measured at different transistor bias points and power dissipations. The amplifier was operated at as low as 0.7mW power dissipation with a measured 8K of noise (or about 0.12dB Noise figure) and 20dB of Gain at 500MHz. The developed amplifier offered good performance at an extremely low cost and with a very short development time, this amplifier can be useful to a variety low temperature physics experiments.