19.MOSFET_digital - 1 MOSFET model summary PSP: 1. 2. 3. 4....

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MOSFET model summary MOSFET model summary PSP: 1. Gradual Channel Approximation - enables solution of Poisson to get Q s 2. Use Q=CV to get another expression for Q s 3. Equate and get implicit expression for φ s (V GB , V DB , V SB ) 4. Charge Sheet Approximation - no V(x) across channel - φ s due to Q b -use±DA 5. DDE for I D 6. Predicts exponential- and power (1-2)-dependence on V GB at low and high V GB , respectively. 7. It is a model for all conditions SPICE: 1. Assumes channel is strongly inverted everywhere. This is not true at the drain for moderate and high V DS , so the model only works in the triode regime. 2. Patch-up the model by assuming I D saturates at the `breakdown' point. 3. LEVEL 1 assumes v = μE x . So I D is overestimated at high E x . 4. LEVEL 49 limits v to v sat , so it gives more a more realistic I D . 5. I D (SPICE) > I D (PSP) because of strong inversion assumption. 6.
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This note was uploaded on 11/10/2010 for the course EECE 480 taught by Professor David during the Fall '09 term at The University of British Columbia.

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19.MOSFET_digital - 1 MOSFET model summary PSP: 1. 2. 3. 4....

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