A waveform with near-instantaneous transitions between its high and low states, producing the sharpest possible field changes per pulse. Square waves maximize slew rate because the field rises and falls as quickly as the hardware allows, generating the strongest induced electric field in tissue for a given peak Gauss. This makes square waveforms the most effective shape for biological stimulation when slew rate is the priority. Achieving a true square wave requires fast switching components and careful circuit design to control ringing and overshoot at the transitions.
The shape of each pulse is its waveform. A sine wave rises and falls smoothly; a square wave snaps between two levels; a triangle wave ramps up and down in straight lines; a sawtooth ramps up then drops sharply. The shape sets how sharply the field changes, which is what the timing measurements capture.
