P. Hakonen, T. Lehtinen, L. Roschier, and M. Sillanpää
In order to reach the quantum limited performance of rf-SET electrometers, preamplifiers with a noise temperature of 100-200 mK are needed. One way to achieve such a sensitivity is to use SQUIDs as amplifiers. We made a design for a SQUID-amplifier for 100 kW sources with 5 MHz band in collaboration with the Microsensing group of VTT Information Technology. According to our simulations, the effective noise temperature of the device is on the order of 150 mK, i.e., by a factor of ten lower than in the HEMT based systems. First experiments using the amplifier indicate a gain of 2 dB in an unmatched configuration, which is slightly more than expected. In matched case, the gain will increase up to 20 dB.