The Canon you noted looks OK but I've also used an 8 or more megapixel camera for such scans. Let's try a little math to see if 8MP is enough?
A4 paper size is at http://en.wikipedia.org/wiki/Paper_size
So if I take my old 8MP 3264x2448 pixel camera and take the 11.7 inch side along the 3264 side, I get the following DPI.
11.7 inch at 278 DPI
8.3 inch at 294 DPI
Since a lot of phones have 8MP cameras and this quality is about double of a fax copy, why are you getting a scanner if these are just notes?
I'm studying math in the university and want to buy a scanner to scan the lecture-notes. I need a cheap yet powerful scanner and I thought about the Canon P-150. I'm writing my notes on a checkered A4 pad (like this one: http://www.stocksnippets.com/previews/StockSnippets-ID10100679-Checkered%20note%20pad.jpg) hence I don't know the thickness of pages. Should this model fit tor that and will be able to scan my notes? Thanks.