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This article discusses the design and measurement of high temperature superconductor transimpedance amplifiers using bi-crystal junction SQUID arrays. The peak to peak modulation voltages of the arrays as a function of their SQUID inductance were measured. The measured transresistance, dV/sub o//dI/sub i/, of a 30-element array of 5-pH SQUIDs was 4 V/A. The voltage modulation depth of the 30-element array was 2 mV and the white noise of the array was 1.0 nV/Hz/sup 1/2/ at 100 kHz. The dynamic range of the array was 120 dB in a one hertz bandwidth. This device has the potential to be used as a broadband amplifier for low impedance sources.

We measured the V-/spl Phi/ of 100-element SQUID arrays and compared them to simulations. Two SQUID inductances, 13 pH and 5 pH were studied. The change of voltage modulation depth per /spl Phi//sub 0/ in a 5 pH SQUID array was faster than that in a 13 pH SQUID array due to larger effective area variations. The effect of magnetic field uniformity on the SQUID arrays output was also studied. We found that a non-uniform magnetic field had the effect of reducing the output voltage and periodicity in V-/spl Phi/ for a SQUID array with high flux bias. >

A 7104-element serially connected SQUID array magnetometer has been designed and tested. The array had a measured magnetic field to voltage transfer function dV/dB of 1.2/spl times/10/sup 5/ volt/Tesla and a peak to peak modulation voltage of 0.6 volt. The sensitivity of the array magnetometer is 105 fT/Hz/sup 1/2/ at 20 kHz, and is limited by the 1/f noise of SQUIDs. The effective signal collection area of the array is 0.018 cm/sup 2/. The measured dynamic range of the array is 126 dB.