Lecture 4_0916

6 coffee cart analogy tired student runs from vlsi

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Unformatted text preview: Theory CMOS CMOS VLSI Design 4th Ed. 6 Coffee Cart Analogy Tired student runs from VLSI lab to coffee cart Freshmen are pouring out of the physics lecture hall Vds is how long you have been up – Your velocity = fatigue mobility Vgs is a wind blowing you against the glass (SiO2) wall At high Vgs, you are buffeted against the wall – Mobility degradation At high Vds, you scatter off freshmen, fall down, get up – Velocity saturation • Don’t confuse this with the saturation region 4: Nonideal Transistor Theory CMOS CMOS VLSI Design 4th Ed. 7 Mobility Degradation High Evert effectively reduces mobility – Collisions with oxide interface 4: Nonideal Transistor Theory CMOS CMOS VLSI Design 4th Ed. 8 Velocity Saturation At high Elat, carrier velocity rolls off – Carriers scatter off atoms in silicon lattice – Velocity reaches vsat • Electrons: 107 cm/s • Holes: 8 x 106 cm/s – Better model 4: Nonideal Transistor Theory CMOS CMOS VLSI Design 4th Ed. 9 Vel Sat I-V Effects Ideal transistor ON current increases with VDD2 Velocity-saturated ON current increases with VDD Real transistors are partially velocity saturated – Approximate with -pow...
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This note was uploaded on 01/22/2014 for the course ECE 261 taught by Professor Morizio,j during the Winter '08 term at Duke.

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