Lec19 MOSFET threshold

Lec19 MOSFET threshold - EECS 320 MOSFET Threshold MOSFET...

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EECS 320 MOSFET Threshold MOSFET Structure The Idea: Control current flow from source to drain using applied gate voltage Our MOS analysis showed that charge at Si/SiO 2 interface is strongly dependent on V G The resistance from source to drain will vary with this charge in the “channel”
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Band Diagram Cross section in channel Create inversion layer in channel for current conduction More Band Diagrams Band diagram in inversion What does PMOS look like? Band diagram along channel
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Review of Bias Effects - - - - - - - - -+ h + h + h + h + h + h + h + - - h + h + - - h + h + e - e - e - e - e - e - e - e - e - e - MOSFET Threshold Voltage Define condition where channel charge is significant ρ MO S q φ F q φ s Define where inversion charge at SiO 2 /Si equal to depletion charge Mathematically, φ S =2 F = i A F n N q kT ln ox F A S F MS T C N q V ε 4 2 + + = ox F D S F MS T C N q V 4 2 = = i D F n N q kT ln NMOS PMOS Need to also account for oxide and interface charges, if present
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Lec19 MOSFET threshold - EECS 320 MOSFET Threshold MOSFET...

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