Circuit demonstrating the importance of a proper FET driver at high frequencies. A 1nF capacitor represents the gate capacitance of a standard NFET. A 5V pulse and series 250 ohm resistor represents a 20mA limited 5V digital logic pin. The push-pull transistor stage decouples this resistance of the logic source from the capacitance of the gate, allowing the gate to be driven more quickly than if the logic source is connected directly to the gate, which by itself, forms an RC low pass filter which attenuates the higher harmonics (and thus fast edges) of the logic pulse.
