Wireless neural stimulator with injectable

A neuromodulation system, comprising:

• one or more injectable microstimulators comprising a length of 10 mm or less, a diameter between 0.5 mm and 3 mm, and lacking a battery;
• and
• an external free running resonance magnetic field generator, comprising:
• a coil:
• a capacitor connected in parallel with the coil such that a stimulation signal is a portion in time of a resonance between the parallel capacitor and coil;
• a DC power supply at a first side of the parallel capacitor and coil, and configured to activate the parallel coil and capacitor;
• a switch to ground on a second side of the parallel capacitor and coil, wherein the switch comprises a transistor and a rectifier;
• and
• a microprocessor configured to turn off a gate or a base of the transistor just prior to a first series of decaying resonant pulses to provide a free running resonance between the coil and the capacitor and then turn on the gate or base to build up a current in the magnetic field generator prior to a second series of decaying resonant pulses to reduce electrical energy in the coil between the first and second series.