The output of the oscillator is a series of electrical pulses that are typically in the range of 1 to 300 Hz. The open-circuit voltage across the electrodes is typically in the range of 1 to 60 volts, but is current-limited to values that are typically less than 500 uA. These levels are sufficient to provide a safe therapeutic response to the user. The embodiment shown here uses a Clare CPC1824 photovoltaic array and a Texas Instruments LPV7215 comparator configured in a standard oscillator circuit. Other embodiments could use other forms of photovoltaic array. The embodiment shown here is a flat, circular device with a diameter of less than 15 mm and a thickness of less than 5 mm. This makes it well suited as a wearable device that can remain in place for long periods while the user goes about their normal activities.
