Progress at NIST on DC SQUID Microwave Amplifiers

We report on the development at NIST of microwave amplifiers using DC SQUIDs. Our design approach is to use small SQUIDs which can be modeled as lumped element circuits, thus separating the design process for the SQUID from that of the microwave impedance transformers. We present our model of the impedance, gain and noise of such a SQUID and measurements of the characteristics of our amplifiers.