The invention provides a method and circuit for forming an electrotherapy current waveform. A charge storage device located externally of a patient's body is charged, and is discharged through the patient's body through at least two discharge electrodes connected by electrical circuitry to opposite poles of the charge storage device. A continuous discharge of the charge storage device through the electrodes is controlled so as to produce at least one phase of a current waveform that includes a ripple. The ripple has a height less than one-third of the height of the peak current of the phase, and the difference between the peak current of the phase and the lowest current of the phase is less than one third of the peak current of the phase. The current waveform has a sensing pulse portion that is integral with the therapeutic discharge portion of the current waveform.