My device has sinking output (Vcc=3.3V), the LED current (and voltage) is controlled by another device (a voltage controlled constant current source) as indicated at VLED. The LED IV curves (as measured) appear below. I am using both, on two different outputs. The forward current for both is 100mA. It is important to be able to maximize the LED output by allowing as close to 100mA as possible. What type of mosfet or transistor and resistor pull-ups or pull-down arrangement can I use? I have viewed many other articles but none seem to address current controlled elsewhere.
With the LED current properly controlled by the external source, all you need is something to sink up to 100mA effectively. Something like this:
Replace Q1 with a low Vgs MOSFET if you want to waste less current through R1.