Answer Happy

Q2 (a) Describe the main features of the design and operation of a MOS transistor and state the difference between the two transistor types. Your description should include a labelled sketch of a MOS transistor cross-section, a brief explanation of the terms depletion and inversion and their role in enabling voltage control of the channel resistance. (7 marks) Q2 (b) State the four main indicators used to determine MOS transistor performance. From the standard MOS equation, outline the strategy to improve transistor gain. With regard to power density, what is the disadvantage of reducing the MOS transistor dimensions and what additional changes can be made to offset this. Page 2 of 9 (4 marks) Q2 (c) Sketch the structure of a single molecule phototransistor based on a protein molecule, label the main components and state the function of each. Describe the photoresponse characteristics of the gate quantum dot and from this explain how this device can act as a transistor. How is the selective attachment of protein to the electrodes achieved? (7 marks)