Half bridge using n-channel MOSFETs yeah, just don't use this design: http://electronics.stackexchange.com/questions/56140/driving-low-side-of-a-mosfet-bridge-with-3-3v Inputs being 3.3V, it's not enough to polarize even the bottom FET, hence the bottom driving circuitry too. Inputs are complemented. There is a pull-up (remember it's complemented) resistor on the low side, avoiding short circuit when there is no input.