retrolefty:
I was just noting that the resistor isn't required for the MOSFET example logic level mosfet switch to work switching an LED.
Not sure I understand that either. While one doesn't need a gate resistor using a mosfet (although many recommend a small one) there is still a need for a series resistor in the led/drain circuit to limit led current when the mosfet is full on.
A current limiting resistor is required when the LED is always on, or on with a high duty cycle. If the LED is on, say 50%, of the time you can get away with a current a little less than twice the maximum rated on the data sheet. If, as in my example, the LED is on for 10uS out of every 15-20 seconds, then no no current limiting resistor is needed, and the LED can receive more than 5+ amps and survive.
In the eighties, Forest Mims, had an article about using an original 20mA IR LED with low duty cycle pulses of 1+ amps to significantly increase the transmission distance.