Systems and methods for closed loop control to ensure a constant current output with a changing load resistance

A stimulator with a low output impedance, the stimulator comprising:

• a voltage source configured to generate an input voltage waveform;
• a variable gain voltage amplifier configured to receive the input voltage waveform from the voltage source and provide an output voltage to a load;
• and
• a feedback component, coupled to a current return of the adjustable gain amplifier, comprising a set point voltage source configured to generate a set point voltage and an amplifier configured to compare an output of a current power detector circuit to the set point voltage,
• wherein the feedback component is configured to determine the voltage delivered to the load by sampling current into the load over a time period, estimating a power based on the current into the load over the time period, and
• wherein a gain of the adjustable gain amplifier is adjusted based on a difference between the output of the current power detector and the set point voltage so the current power output to the load remains constant.