The magnetic response of superparamagnetic iron oxide nanoparticles (SPIONs) varies significantly during nucleation and growth, requiring adaptive signal conditioning to avoid saturation and maintain sensitivity. This work presents the design and experimental characterization of a low-noise variable gain amplifier (VGA) based on the AD603 for this application. The VGA offers a pin-selectable gain range from ?10 dB to +30 dB, enabling high gain at early synthesis stages and controlled attenuation at later stages. Performance was evaluated in terms of transient response, gain, phase behavior, and noise characteristics over a frequency range of 1 kHz to 1 MHz. Measurements demonstrate stable gain, limited phase variation, and improved noise performance through parallel amplifier configurations, indicating suitability for low-noise, high-dynamic-range SPIONs measurement systems such as MPS/MPI devices.
Malhotra et al. (Thu,) studied this question.