Low-Cost, Low-Power Gradient Amplifier for MRI Array Coils Using Modified Audio Class-D Amplifiers and Custom Analog Feedback

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.