I am working on a project using the cyclone V from Altera. The FPGA has 3.3v GPIO pins and I would like to know what I could use to mimic a GPIO pins output. I am using LTspice and I cannot find any relevant information. It would appear that a low ~10-100 ohm series would be close. We are driving mosfets and transistors at high frequencies. Does anyone have any suggestions?

1. FPGA output driving gate of MOSFET ? 

It would be wise to use a speciality MOSFET driver and drive the inputs of the driver from FPGA GPIO. FPGA GPIO need not be modelled instead driver could be modeled and you would have to check with the vendor for spice models.

2. Series termination - If the switching frequency is considerable (> 20 MHz or so) a series resistor of about 80 ohms would be required, this could be simulated in Spice.