That's an interesting question. I guess the truth is all of my main characters are a little bit me -- and all of them are a lot NOT me. :-) I'm not sure if that makes sense, but what we write is limited by our education, experience, imagination. If we can't conceive of it, we can't create it. So in that sense we -- every writer -- is always writing what he or she "knows."
I would say the characters who probably most share my real life "voice" are Adrien English and Kit Holmes. But of course they are not me, and they even they hold opinions and have ideas that I don't always agree with!
To make a character interesting you have to be sure to give them their share of real fears and real flaws -- and of course I have none! :-P