MOSFET Gate Charge Calculator

A MOSFET switching circuit wastes power through conduction, switching, and gate charging — and quantifying each loss is critical for thermal design and efficiency optimization. Enter your Bus Voltage, Drain Current, Switching Frequency, Duty Cycle, Gate Charge (QG), RDS(on), Output Capacitance, and switching times into the MOSFET Gate Charge Calculator to get Total Power Loss. Secondary outputs break this down into Conduction Loss, Switching Loss, Gate Charge Loss, Average Gate Current, and Gate Driver Power.

V
A
Hz
%
V
nC
mΩ
pF
ns
ns
ns
ns

Results

Total Power Loss

--

Conduction Loss

--

Switching Loss

--

Gate Charge Loss

--

Average Gate Current

--

Gate Driver Power

--

More Electrical & Electronics Tools

Frequently Asked Questions

What is gate charge and why is it important for MOSFET switching?

Gate charge (QG) is the amount of electrical charge required to turn on a MOSFET. It determines the switching speed and gate driver current requirements. Higher gate charge means slower switching and more power loss.

How do I calculate the required gate driver current?

Gate driver current equals gate charge times switching frequency (IG = QG × fSW). This determines the minimum current capability needed from your gate driver circuit.

What are the main sources of power loss in a MOSFET?

The three main power losses are: conduction loss (I²R loss when ON), switching loss (during transitions), and gate charge loss (energy to charge/discharge the gate capacitance).

How does switching frequency affect MOSFET power losses?

Higher switching frequency increases both switching losses and gate charge losses proportionally, while conduction losses remain constant. This is why high-frequency applications require MOSFETs with low QG and fast switching times.

What is RDS(on) and how does it affect power loss?

RDS(on) is the drain-source resistance when the MOSFET is fully ON. Conduction power loss equals I²D × RDS(on), so lower RDS(on) reduces power dissipation but may increase gate charge.

How do rise and fall times impact switching losses?

Longer rise and fall times increase switching losses because the MOSFET spends more time in the linear region where both voltage and current are present simultaneously.

What gate drive voltage should I use for my MOSFET?

Use the gate voltage specified in the datasheet for rated RDS(on), typically 10V for standard MOSFETs and 4.5V for logic-level devices. Higher voltage reduces RDS(on) but increases gate charge losses.

How does output capacitance (Coss) affect MOSFET performance?

Coss creates additional switching losses as it must be charged/discharged during each switching cycle. The energy loss per cycle is 0.5 × Coss × VDS², multiplied by switching frequency.