My IC designer buddy Don Sauer already has something like 40 patents, mostly when he worked at National Semiconductor. Now he is working up an article for me on how to do it cheap. He indicates you can get one filed for about 400 dollars and if it is accepted it might cost as much as 2000 dollars. Of course, all this is predicated on your making sure that you don’t hire a lawyer. That can easily add an order of magnitude, or two,  to the cost. Don sent a list of some of his favorite patent websites: