Lecture9-MOS_Transistor-6up

Lecture9-MOS_Transistor-6up - EE141-Fall 2010 Digital...

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EE141 1 EECS141 1 Lecture #9 EE141 EE141 -Fall 2010 Fall 2010 Digital Integrated Digital Integrated Circuits Circuits Lecture 9 Lecture 9 MOS Transistor Model MOS Transistor Model EE141 2 EECS141 2 Lecture #9 Announcements Announcements ± Lab #4 this Fri., next Mon. ± Homework #4 due today ² Homework #5 due next Thurs. ± Midterm #1 Thurs. Oct. 7 th ² Location TBA EE141 3 EECS141 3 Lecture #9 Class Material Class Material ± Last lecture ² LE in decoders ± Today’s lecture ² MOS transistor modeling – Will see how to use these models to understand tradeoffs between CMOS gate delay, power, etc. ± Reading (3.3.1-3.3.2) EE141 4 EECS141 4 Lecture #9 MOS Transistor MOS Transistor EE141 5 EECS141 5 Lecture #9 n + p -substrate D S G B V GS + Depletion region n -channel n + Threshold Voltage: Concept Threshold Voltage: Concept ² With positive gate bias, electrons pulled toward the gate ² With large enough bias, enough electrons will be pulled to "invert" the surface (p n type) ² Voltage at which surface inverts: “magic” threshold voltage V T EE141 6 EECS141 6 Lecture #9 The Threshold Voltage i A T F n N ln φ = φ ± Threshold ± Fermi potential 2 Φ F is approximately 0.6V for p-type substrates γ is the body factor V T 0 is approximately 0.45V for a 0.25um process () 0 22 TT FS B F VV V γϕ ϕ =+ + − Depletion charge 2 B TF B F ox Q V C ϕϕ =+ +
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EE141 7 EECS141 7 Lecture #9 n + n + p -substrate D S G B V GS x L V ( x ) + V DS I D Transistor with Gate and Drain Bias Transistor with Gate and Drain Bias EE141 8 EECS141 8 Lecture #9 The Drain Current The Drain Current () i Qx = ± Charge density: ± Velocity: D I = n x υ = ± Current: EE141 9 EECS141 9 Lecture #9 Solving the Drain Current Solving the Drain Current ± Integrate along the channel: EE141 10 EECS141 10 Lecture #9 Plot of I Plot of I -V Curve V Curve ± Is this really what happens?
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This note was uploaded on 02/06/2011 for the course EE 141 taught by Professor Staff during the Spring '08 term at University of California, Berkeley.

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Lecture9-MOS_Transistor-6up - EE141-Fall 2010 Digital...

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