Gradient System: Gradient Amplifiers

Gradient System · Electronics

Delivering hundreds of amperes into an inductive load, switching in tens of microseconds, once per element.

End face of a magnet with a ring of small amplifier modules and their wiring — Many small amplifier modules instead of three large ones, mounted close to the coil. Illustration.

Gradient array power amplifier controller circuit board — The controller module of our gradient array power amplifiers (version 3.0, 2024), with its FPGA module.

Two green amplifier circuit boards with GaN transistors inside an aluminum enclosure — Two gallium nitride amplifier boards in their enclosure (October 2026).

The question

A gradient coil is an inductor, and driving it quickly means forcing current against that inductance with a large voltage. A conventional system has three such amplifiers, one per axis. An array has as many as it has elements, which turns a problem of building three very large amplifiers into a problem of building many smaller ones that must share a supply, stay synchronised, and not interfere with each other or with the receive chain.