Driving a brushless DC (gimbal) motor can be a pain in the transistors. [Ignas] has written up a nice article not only explaining how to do just this with an Arduino, but also explaining a little ...

Transistor Q2 acts as a differential amplifier. It takes the voltage across the motor and shifts its level. D2 blocks the reverse flow of current. D3 closes the motor circuitry for its backrush ...

The efficient high-current operation of the new bipolar transistors from Zetex Semiconductors meets all the performance requirements of dc motor ... medium power motor drive circuits.