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.

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