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I am trying to choose an H-bridge to allow the use of logic for basic directional control of a three volt brushed DC motor (not PWM signals), however they all seem to have minimum voltages above what I need.

Am I thinking of this wrong? I was thinking of the L293 series drivers, however they have minimum voltages around 4.5v which is too high and also low current limits (0.6-1A). This is the motor I have http://uk.rs-online.com/web/p/dc-geared-motors/4130600/

Would I have to build one using MOSFETS to allow operation at this voltage, because obviously it is easier to use a pre-built IC? Or would the L293 series be lenient and allow me to supply them with 3v so that they run at this level.

Thanks for any responses and I'm sorry if I've missed anything.

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    \$\begingroup\$ You want to avoid bipolar (including darlington) transistor bridges like the L293 / L298 in low voltage systems, because even if they operate you'll drop a volt or two just across the bridge's transistors. This has been exclusive MOSFET territory for a decade or two now, typically integrated in an IC for moderate voltage / current. \$\endgroup\$ Jul 7 '18 at 19:58
  • \$\begingroup\$ Although most mosfets would need about 4.5+ volts to turn on, that doesn't mean they couldn't switch 3V to run the motor just fine. Do you need to turn them on and off with 3V digital io? \$\endgroup\$
    – Akh
    Jul 7 '18 at 20:33
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There are H Bridge Driver ICs which operate on 3V. Quick search on eg. Digikey or Mouser etc. will get you results. Alternatively you could use a H Bridge Driver ic to drive external mosfets (for power scalability for example or to use the H Bridge series you mention with a 3V supply for the motors).

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It's actually hard to find a good h-bridge for 3V and under because transistors drop voltage. So you either have to account for this by using a higher voltage through your h- bridge, or find chips especially made for low voltage output.

After a bit of searching, I found the drv8835, drv8836, and drv8838 chips worked for 3V and around 1A. I believe the 8838 has a breakout board on pololu and meets your specifications the best. Otherwise, there are surface mount chips.

If you need a high enough current, it might work to drop the voltage after the h-bridge with a couple buck converters. However, that's somewhat expensive, and I'm curious what motor requires 3V and so many amps.

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    \$\begingroup\$ No, you do not want buck converters after a bridge... that is a frankly terrible idea, especially as the whole point of an H-bridge is to be able to drive with either polarity. In actual practice, one can typically just use a somewhat higher drive voltage and apply PWM to moderate the resulting motor speed. \$\endgroup\$ Jul 7 '18 at 19:57

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