Electronic – Is it possible to build an H-Bridge with only N-MOSFETs (and these other components)


I am trying to design an H-bridge circuit and I am only given the following components:

  • Opamp
  • Zener Diode
  • Resistor
  • Capacitor
  • Diode
  • 2-input NOR
  • 2-input NAND
  • Infra-red Detector
  • Infra-red Emitter
  • D flip-flop

I know that it is easy to design an H-bridge using 2 P-MOSFETs and 2 N-MOSFETs, but I am not given P-MOSFETs.

Is there an equivalent circuit for only N-MOSFETs?

Best Answer

If you have a single-output power supply and only NMOS and NPN transistors available, you'll certainly be able to build an "H" bridge, using either, (or both) but you'll not be able to saturate the high side devices so, depending on what your load looks like, they (the high side transistors) may get too hot for comfort and your load probably won't perform the way you want it to.

However, with all the stuff you have available you could easily build a charge pump and use it generate a voltage higher than your supply voltage.

Once you did that you'd be able to drive either the gates of the high-side MOSFETs or the bases of the high-side BJTs at higher than your supply voltage and get the H bridge to work properly.