1. STMicroelectronics, Stradale Primosole 50, 95121 Catania, Italy
2. Ecole Polytechnique Federale de Lausanne, CH-1015 Losanne, Switzerland
3. Department of Electronics and Telecommunications, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129 Torino, Italy
4. Laboratory of Integrated Circuits, École Polytechnique Fédérale de Lausanne, CH-2002 Neuchâtel, Switzerland