Here is the link to simulation of h bridge that I built Simulation link in this I was somehow able to control transistors with 5 volts when supply was 9 volts h bridge but I still didn't completely understand it as for current to flow base voltage has to be .7v higher than emitter voltage, so I simulated only one transistor of circuit and it didn't work which means the 5 volt at base of transistor wasn't able to activate transistor Simulation of only one transistor

only on transistor of h bridge

So can someone please explain me how the first circuit works but second doesn't and is there a way to control transistor with lower base voltage without overcomplicating circuit with something like bootstrapping circuit

  • \$\begingroup\$ Your single-transistor simulation doesn't have a ground. \$\endgroup\$
    – Hearth
    Commented May 9, 2021 at 12:58
  • 2
    \$\begingroup\$ Why did you delete your old question and create a nearly identical one? Next time, you should edit your original question. \$\endgroup\$ Commented May 9, 2021 at 13:09
  • \$\begingroup\$ Your proposed circuit opens at >1.4v input since you have two BE junctions in series. Its no problem to controll circuit like this without bootstraping until you have PNP in high side - they opens with zeros (or exactly < Vcc-0.7) and close with Vcc (9v). \$\endgroup\$
    – user208862
    Commented May 9, 2021 at 13:59

1 Answer 1


This won't work: -

enter image description here

Your circuit does not have a ground connection and hence there is no current return path to the 5 volt negative/neutral terminal. This means no current into the base of either transistor.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.