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VLSI Design

VLSI Design. Rehan Azmat Lecture 4 Devices. Previous Lecture. Semiconductor Theory Diode BJTs FETs MOSFETs. Lecture 4. MOSFET Static Behavior. N-MOS Transistor. MOS Symbols. MOS Static Behavior. The Threshold Voltage Resistive Operation The Saturation Region

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VLSI Design

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  1. VLSI Design Rehan Azmat Lecture 4Devices

  2. Previous Lecture • Semiconductor Theory • Diode • BJTs • FETs • MOSFETs

  3. Lecture 4 • MOSFET Static Behavior

  4. N-MOS Transistor

  5. MOS Symbols

  6. MOS Static Behavior • The Threshold Voltage • Resistive Operation • The Saturation Region • Channel-Length Modulation • Velocity Saturation • Drain Current versus Voltage Charts • Subthreshold Conduction

  7. The Threshold Voltage • Width and Space charge per unit area is given as: NA issubstrate doping and Ø is the voltage across the depletion region

  8. The Threshold Voltage.... • Strong inversion occurs at 2 times of Fermi Voltages. Where Fermi voltages is • Charge stored in depletion region is • VSB effect charge stored in depletion region. Above equation becomes • VSB effect also effect threshold voltages

  9. Resistive Operation • The induced charge per unit area at point x is Where • Current is equal to product of drift velocity of the carriers and available charge.

  10. Resistive Operation... Where Then By integrating Where

  11. The Saturation Region At ID becomes

  12. Channel-Length Modulation Where lambda is channel length modulation

  13. Velocity Saturation

  14. Velocity Saturation...

  15. Drain Current versus Voltage Charts

  16. Drain Current versus Voltage Charts…

  17. SubthresholdConduction Slope Factor: How much VGS has to be reduced for the drain current to drop by factor of 10.

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