I've controlled a motor going one direction using only one transistor. With an H Bridge, I can make a motor go forward, backward and brake. Does an H Bridge have only three transistors inside it to perform these functions, or does it take a larger number?

  • Minimum four transistors required in a H-Bridge – Chetan Bhargava Jul 18 '15 at 5:09
  • Some use darlington pairs, so 8 transistors instead of 4 – Gerben Jul 18 '15 at 13:07
  • Notionally 4 "switches". Name motor terminals left and right - then switches are left+ left- right+ right-. Switch left+ and right- on and motor rotates one way. OR switch left- and right+ on and motor goes other way. Draw a diagram and be SURE it makes sense. | In some special cases you can us ONLY 2 switches- say left+ and left- AND two resistors from right to + and - OR a split supply with motor centre connected to supply mod point. THEN left+ only makes motor go one way and left- only makes it go the other way. In most cases this is not a viable arrangement but sometimes it is useful. . – Russell McMahon Jul 18 '15 at 14:01

The absolute minimum number of transistors in a H bridge is 4 (one in each leg of the "H" and the motor in the middle), but there may be more depending on what voltage and control scheme is desired.

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