Are the Trinity and the Hebrew God the same?

Dr. Jacobs presented a very interesting question to our class this morning. He expressed that Jews and Christians do not have the same God. His explanation for this claim was that, in Christianity Jesus and God and the Holy Spirit are all God, while in Judaism there is only God. So the question he asked was this, "If the Christian God has to have all three parts, and the Hebrew God does not involve Jesus or the Spirit is it the same God?" This question completely took me by surprise, because, as growing up in a liberal church setting, the idea that Jews and Christians shared a God had been totally ingrained in my way of thought. I have put a lot of thought on this theory and have yet to decide what my position is. Hopefully I come back to this subject and do some research on what others have to say.