Powered magnets presently provide the highest magnetic fields for nuclear magnetic resonance (NMR) applications. A critical component of powered magnet systems is a feedback system that reduces temporal field fluctuations in the magnet caused by power supply ripple and variations in the flow rate and temperature of cooling water. The objective of this project is to improve the performance of a closed-loop flux regulator that utilizes a pickup coil to sense field fluctuations. As the voltage across the pickup coil is proportional to the derivative of the field fluctuations, the system uses an integrating preamplifier to recover field fluctuations. The existing integrating preamplifier is realized using analog electronics that causes the integrator output to drift. In turn, the feedback controller produces an undesirable drift in the magnetic field. This work aims to reduce the drift by designing a digital integrating preamplifier realized using a field-programmable gate array (FPGA).