SQUID Current Sensor With Differential Output

We have developed a superconducting quantum interference device with differential output (diffSQUID). The device concept aims at improving the operability of SQUID current sensors in the presence of large common-mode signals. The diffSQUID is based on a series connection of two identical SQUID sensors. The biasing and input signal coupling provides for the differential output signal. The diffSQUID is read out by a fully differential amplifier. A compact, low-power, and low-noise differential amplifier has been developed for this purpose. This amplifier is partially powered via the diffSQUID´s combined bias and output signal leads and can be operated at temperatures between 77 and 300 K.