Efficient precision current regulator for low-voltage magnets

A simple, inexpensive current regulator has been built using power transistors and a chopper amplifier to regulate magnet currents to <0.001%. Thus far, the regulator has been used to 20 amp and 40 v, and at ∼100 amp and ∼200 v. With minor modifications, it will give very much better regulation. © 1958 The American Institute of Physics.