1
\$\begingroup\$

If we have an H-bridge made of 4 N-MOSFETs, the gate voltage applied to each pair must be different because in an active circuit the sources will have different voltages. How much?

\$\endgroup\$
2
  • 2
    \$\begingroup\$ The difference will be approximately that of the value of the DC supply feeding the bridge. \$\endgroup\$ – Andy aka Apr 7 at 13:23
  • \$\begingroup\$ For large supply voltages, grossly exceeding typical \$V_{GS}\$ of MOSFETs, high-side driver ICs take care that the high-side MOSFET gates are driven with respect to the local Source Voltage \$\endgroup\$ – tobalt Apr 7 at 13:31
2
\$\begingroup\$

This assumes an on-off type H-bridge and not a linear H-bridge used in bridge tied audio amplifiers.

How much?

If you ignore protection features (required to limit gate-source voltages when the supply exceeds the maximum gate-source voltage), to efficiently drive current through the load requires these gate voltages to be present: -

enter image description here

And clearly, the difference in voltage between the two driven gates for the MOSFETs that are activated is just the supply voltage.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

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