Is a high drive current necessary for power MOSFETs?

Power-on MOSFET generally do not require large drive-current. However, pay attention to the current drive capability,in the case of high-speed switching.

Bipolar transistors require a large base current to maintain a low on-state voltage. However, MOSFET is a voltage-controlled device, so it can be driven with only small amount of power to charge the gate. However, since the input capacitance Ciss of the powered MOSFET is somewhat large, the input capacitance must be charged quickly with a low-impedance drive circuitry, particularly for high-speed switching.

As a guide to the gate-current required for recharging, the drive-current can be calculated simply from Qg properties specified on the datasheet. If the required switching-time is t (desired), for example ton or toff, then:
Ig=Qg/t(desired)

Fig. 1: Parasitic capacitance of MOSFET
Fig. 1: Parasitic capacitance of MOSFET
Fig. 2: Measuring circuit of the switching circuit
Fig. 2: Measuring circuit of the switching circuit

The application note "Electrical characteristics: Power MOSFET application note" has charge-capacitance characteristics. Please also refer to this.

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