Low Noise and Low Power Co Amplifiers for Onsala and

instrumentation activities, several low noise, low power consumption cryogenic amplifiers were developed for frequencies between 2 and 9 GHz based on GaAs HEMT MGFC4419G from Mitsubishi. Two narrow-band amplifiers were designed, one for 3.4-4.6 GHz with 2.7 K noise temperature and 30 dB gain, the other for 8.0-9.0 GHz with 5 K noise temperature and 26 dB gain, at 12 K ambient temperature. A broadband amplifier for 4-8 GHz demonstrates 5 K noise temperature and a gain of 26 dB with 2-stages, and 34 dB with 3-stages. Lastly, a 2-4 GHz amplifier is under current development. These amplifiers are currently used at the Onsala 20 m and 25 m telescopes, Sweden, both as front-end amplifiers and as IF amplifiers for mm-wave receivers and will also be used in the new APEX sub-millimetre telescope in Atacama Desert, Chile. I