My boy frequently stays at my mother's house with her chihuahua, and my brothers who we visit often have a toy poodle. Zeus gets along with them fine however he basically 'ignores' them. He is territorial towards large dogs at the house, and loves to play at parks etc, but he just doesn't think the little dogs are anything to worry about..
Is this chihuahua a male? That may make it impossible for them to ever be unsupervised together.
Definitely start somewhere neutral. Do not 'introduce' them in the house. Have them meet you at the park etc, then move to perhaps the front or backyard if they get along well. Make sure to keep all food, toys, treats, bowls, beds, etc completely out of the question as to make sure the dog is not being protective over ANYthing. Even if your dog is perhaps extremely protective over you, remove yourself from the situation at first and have another family member there. (I had a german shepherd attack my dobe, because the shepherd thought I was 'his' after petsitting for a week. So I know some dogs can be 'possessive' over their humans)... Alot of dogs when introducing to another one, they feel their owner's overwhelming apprehension on the other end of the leash and will therefore be much more assertive, aggressive, dominant, you name it. If you have a fenced in location where you can let the dogs meet on their own, I may recommend that. But this depends on you and the dog. It's just if you're feeling overwhelmed, scared, or nervous about it, your dog is likely to pick up on that and act differently.
With all of this being said, I wouldn't worry too much about the chihuahua being so small. After all, he/she is still a dog. (And I've yet to meet any chihuahua that actually thinks they are smaller than a doberman).
Good luck!
