This research demonstrates a low-cost solution for gradient amplifiers in MRI coils, using Class-D technology and analog feedback to optimize performance.
Motivation: Existing gradient power amplifiers are too powerful and very expensive for gradient array coils with numerous independent channels. Goal(s): A low-cost, low-power gradient power amplifier with digital/analog inputs, designed as an independent voltage-controlled current source for driving gradient array coils. Approach: The frequency response of a commercially available Class-D audio amplifier (TDA7498E) is modified to include DC and then amended by an analog feedback circuit with digital input to control load current. Results: The amplifier drives inductive loads up to 2 ohms + 200 μH with currents up to ±9 amps in less than 50 μs. Impact: Gradient array coils offer tunable magnetic field profiles and adjustable ROIs but require multiple power amplifiers. This work demonstrates an affordable (<90$) solution using commercially available Class-D audio amplifiers combined with tunable analog feedback system to feed multi-channel gradient arrays.
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Takrimi et al. (2025) studied this question.
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