To quickly switch power devices and reduce associated switching power losses, a gate driver is employed between the PWM output of a controller and the gates of a power semiconductor device. Also, gate drivers are indispensable when it is impossible for the PWM controller to directly drive the gates of the switching devices. With the advent of digital power, this situation will be encountered often because the PWM signal from the digital controller is often a 3.3V logic signal which cannot effectively turn on a power switch. Level shifting circuitry is needed to boost the 3.3V signal to the gate-drive voltage (such as 12V) in order to fully turn on the power device and minimize conduction losses. Traditional buffer drive circuits based on NPN/PNP bipolar transistors in totem-pole arrangement, being emitter follower configurations, prove inadequate with digital power because they lack level-shifting capability.

Gate drivers effectively combine both the level-shifting and buffer-drive functions. Gate drivers also fulfill other needs such as minimizing the effect of high-frequency switching noise by locating the high-current driver physically close to the power switch, and reducing power dissipation and thermal stress in controllers by moving gate charge power losses from the controller into the driver.