Gate Driver
A gate driver takes a logic-level input (3.3 V or 5 V) and drives a power transistor's gate with several amperes of peak current to charge and discharge the gate capacitance quickly. Faster switching reduces the time the transistor spends in its linear region, which is where switching losses occur.
A complementary totem-pole output stage (one pull-up, one pull-down transistor) is driven by the input buffer. The pull-up charges the gate through a series resistor and the pull-down discharges it. Bootstrap or charge-pump circuits supply the above-rail voltage needed to fully enhance an N-MOSFET on the high-side of a half-bridge.
In plain terms
A megaphone for gate signals: the microcontroller whispers a logic level and the gate driver shouts it at the power transistor, delivering amperes of peak current to charge the gate capacitance in nanoseconds.
Why designers use it
- Drive the gate of a 60 A MOSFET in a motor H-bridge without excessive transition loss.
- Provide dead-time between high-side and low-side switches to prevent shoot-through.
- Level-shift the gate signal for a high-side N-MOSFET above the supply rail.
- Provide isolated gate drive for the IGBTs in a PV inverter.
Best for
- Motor drives
- DC-DC converters
- PV inverters
Key specifications
- Drive current: 0.5 A – 30 A peak
- Output voltage: 5 V – 30 V
- Propagation delay: 20 ns – 200 ns
- Isolation voltage: 0 V (non-isolated) – 5 kV
- CMTI: 100 – 200 kV/µs (Isolated parts)
When not to use it
- For logic-level MOSFETs in low-current applications where the MCU's GPIO can drive the gate directly.
- When the gate capacitance is so small that a small-signal BJT driver suffices.
Common mistakes
- Ignoring the bootstrap capacitor hold-up time — if the high-side switch stays on too long, the bootstrap cap discharges and the gate voltage sags, turning the FET resistive.
- Driving the gate resistor so low that dV/dt-induced shoot-through triggers the complementary FET.
Where you will find it
- A three-phase brushless motor controller in a cordless drill uses three half-bridge gate-driver ICs to commutate the motor phases: each IC's bootstrap circuit charges during the low-side on-time, then uses that stored charge to pull the high-side N-MOSFET's gate above the 18 V battery rail during commutation.
- A solar microinverter uses isolated gate drivers (with internal transformer) to drive the bridge IGBTs: galvanic isolation is mandatory because the IGBT emitters sit at mains potential while the control logic runs at safe low voltage, and the 1500 V isolation rating keeps the operator safe.
- A Class-D audio amplifier uses a UCC27201A half-bridge driver to switch its output MOSFETs at 400 kHz: the driver's 4 A peak gate current charges the 10 nF gate capacitance in 10 ns, keeping the transistors out of their linear region long enough to achieve 95 % amplifier efficiency.
A short history
A gate driver is a circuit between a low-power controller and a power transistor such as a MOSFET or IGBT. The gate behaves like a capacitor that must be charged or discharged to switch states, and microcontrollers often lack enough current to do this quickly. Gate drivers amplify the signal, enabling faster switching while buffering the controller from the gate's transient current demands.
Good to know
- A SiC MOSFET needs 18 V on the gate to fully turn on with low loss — gate drivers exist precisely because microcontrollers can't deliver that voltage or the 5 A pulses required to charge gate capacitance in nanoseconds.
- A bootstrap capacitor + diode lets a low-side gate driver float its supply rail above the high-side MOSFET source — the simplest way to drive an N-channel high-side switch.
- Modern isolated gate drivers integrate fault detection (DESAT, OCP), deadtime control, and 5 kV reinforced isolation in a single 16-pin part.