I go to a large university where it is difficulty to become close to the professor (hundreds of students per class) but I do know my TAs well. How do I get a letter from the professor or is it possible to have a TA write one for you?
Unfortunately a LOR from a TA will carry very little weight, and may raise red flags at many (most) programs. Try to meet with your professor, be prepared to talk about yourself (having a resume/cv handy isn't bad). You could also bring up that you are in Mr/Ms XYZ TA's section, and that they could attest to your performance outside of the lab scores.
I'd schedule a time to meet with the professor. I went to a large state university too and while they said directly that my letters would not be overly personal they were still happy to write them for me.
I go to a large university where it is difficulty to become close to the professor (hundreds of students per class) but I do know my TAs well. How do I get a letter from the professor or is it possible to have a TA write one for you?