We are confused about what you want. A "Stepper" usually refers to a multi-phase motor drive circuit. A class G amplifier has a ~stepping supply rail but a class H amplifier does not step. A class H amplifier has secondary analog drivers above the lower supply rail. The transition between the lower and upper supply rails is graduated, not switched. And finally, LM311 has very limited voltage capability that makes it unsuitable for use in high power amplifiers. So please elaborate about what you want because it is not clear from your original post.