I reached NVIDIA at a campus career fair. The recruiters were straightforward; they gave candidates a quiz consisting of four questions. If the questions were completed correctly, they might offer a phone interview a couple of weeks later. The quiz covered difficulty levels you might expect from homework or a midterm in some junior electrical engineering courses. I remember one question asked to draw the MOSFETs inside an AND gate. Other questions were from digital circuits. The phone interview was quite easy, asking only conceptual questions with no computations involved.

Moderate, no unexpected questions asked.