I am trying to get this camera's commuincations to work. The spec sheet says it has a 5V TTL for the enable and a 5V TTL for feedback. While TTL are BJT's, couldn't I just use a FET to do this? For the enable, I just have to make sure 5V gets to the input and for the feedback, I just need to make sure I get a FET with a low Threshold voltage. Does that sound like it would work?

 

Broadly speaking, yes, but if its really TTL, then its unlikely that you will get a high enough voltage to drive a MOSFET unless you add a pull-up resistor to the TTL output.

http://www.allaboutcircuits.com/vol_4/chpt_3/10.html