Two-Pole Integrator SQUID Readout Electronics With High Slew Rate and Small Closed-Loop Frequency Response Peak

Direct-readout electronics with high slew rate and small closed-loop frequency response peak is described by using a two-pole integrator for superconducting quantum interference device (SQUID) applications. In our experiment, a weakly damped niobium-SQUID magnetometer with a large flux-to-voltage transfer coefhcient ∂V/∂Φ of about 380 μV/Φ 0 was used to suppress the contribution of direct-readout preampliher noise. A two-stage preampliher was employed, and integrator parameters were optimized to extend the system slew rate, while minimizing the closed-loop frequency response peak. A slew rate of 2.7 Φ 0 /μs (at 10 kHz) is achieved with only 1-dB peak at 50 kHz in closed-loop frequency response, which means higher system stability. This system was verihed by recording undistorted transient electromagnetic held bipolar square-pulse signals, which required high slew rate and broad bandwidth.