Bipolar drives supply steppermotor windings with current waveforms that look like square waves when fully stepping or sine waves when micro-stepping at a high resolution. The waveforms shown in the oscilloscope displays illustrate the drive current in a half-stepping mode, which is two discrete steps for every pulse delivered to the stepper motor over a speed range of 500 to 4000 half-steps/s. Unfortunately, as the step rate increases, less voltage Experts pretty much agree that motor current is proportional to torque output, and voltage is proportional to motor speed, but do you know when this is might not be true? By Daryle Cooper Senior Design Engineer, ElectroCraft Inc., Dover, New Hampshire is available to supply the required winding current.