Nope. You require a 'turbine endorsement'. You most certainly cannot use your plain vanilla PPL to fly a Caravan.
This is true in JAA land. You need a Cessna SET Class Rating as Whopity mentioned earlier.
In FAA land though you CAN (in theory) fly a Caravan on a plain vanilla PPL. Being less than 12,500 lbs it is covered by the ASEL (Airplane Single Engine Land) Class Rating. You would require a high performance endorsement which you can get from an instructor after training in any aircraft with more than 200 horse power.
The reality of course is that most insurance companies wouldn't let a PPL with no turbine time anywhere near a Caravan unless they had completed an approved course on the type.